Questions & Answers
ICSE - Grade - 9
Subject: Physics
Chapter - 05 - Upthrust in fluids, Archimedes’ Principle and Flotation
Types of Questions
MCQ
- The upward force exerted by a fluid on a body immersed in it is called
a) Weight
b) Pressure
c) Upthrust
d) Force of gravity
Answer: c) Upthrust - The SI unit of upthrust is
a) g/cm³
b) N
c) N/m²
d) kg/m³
Answer: b) N - Buoyancy acts in which direction?
a) Downward
b) Horizontally
c) Upward
d) Along the weight
Answer: c) Upward - The upthrust on a body increases with
a) Increase in weight of body
b) Increase in volume submerged
c) Decrease in fluid density
d) Time of immersion
Answer: b) Increase in volume submerged - For the same volume of body, the upthrust is greater in
a) Oil
b) Water
c) Mercury
d) Kerosene
Answer: c) Mercury - The point where upthrust is considered to act is called
a) Centre of mass
b) Centre of gravity
c) Centre of buoyancy
d) Centre of pressure
Answer: c) Centre of buoyancy - A body floats in a liquid when
a) Weight > Upthrust
b) Weight < Upthrust
c) Weight = Upthrust
d) Volume = Density
Answer: c) Weight = Upthrust - A body sinks in a fluid when
a) Density of body > Density of liquid
b) Density of body < Density of liquid
c) Weight = Upthrust
d) None of these
Answer: a) Density of body > Density of liquid - The apparent loss of weight of a body immersed in liquid is equal to
a) Actual weight of body
b) Weight of displaced liquid
c) Upthrust + Weight
d) Volume of body
Answer: b) Weight of displaced liquid - Archimedes’ principle is used to determine
a) Speed
b) Pressure
c) Relative density
d) Distance
Answer: c) Relative density - According to Archimedes’ Principle, the upthrust is equal to
a) Weight of liquid displaced
b) Volume of liquid displaced
c) Density of liquid
d) Pressure in liquid
Answer: a) Weight of liquid displaced - Apparent weight of a body in a fluid is
a) Actual weight + Upthrust
b) Actual weight – Upthrust
c) Upthrust – Actual weight
d) 0 always
Answer: b) Actual weight – Upthrust - Which body experiences greater upthrust in water?
a) A small stone
b) A wooden log
c) An iron cube of same size
d) All experience same upthrust if volume submerged is same
Answer: d) All experience same upthrust if volume submerged is same - The density of water at 4°C is
a) Minimum
b) Maximum
c) Zero
d) Constant at all temperatures
Answer: b) Maximum - The SI unit of density is
a) g/cm³
b) kg/m³
c) N/m²
d) kg/m²
Answer: b) kg/m³ - Relative density has
a) SI unit same as density
b) No unit
c) Unit N/m²
d) Unit g/cm³
Answer: b) No unit - Relative density =
a) Density of substance / Density of water
b) Volume of substance / Volume of water
c) Mass / Volume
d) Weight / Upthrust
Answer: a) Density of substance / Density of water - A body of density 0.8 g/cm³ floats in water. Its relative density is
a) 0.8
b) 1.2
c) 8.0
d) 80
Answer: a) 0.8 - A solid floats when
a) Density of solid = Density of liquid
b) Density of solid < Density of liquid
c) Density of solid > Density of liquid
d) No relation with density
Answer: b) Density of solid < Density of liquid - If a body weighs 10 N in air and 6 N in water, upthrust is
a) 16 N
b) 10 N
c) 4 N
d) 6 N
Answer: c) 4 N - The principle of flotation states that a body floats when
a) Weight of liquid displaced < Weight of body
b) Weight of liquid displaced = Weight of body
c) Volume displaced = Volume of body
d) Density of body = Density of air
Answer: b) Weight of liquid displaced = Weight of body - An iron nail sinks but an iron ship floats because
a) Nail is small
b) Ship has hollow shape increasing volume
c) Ship is lighter than water
d) Nail is denser than iron
Answer: b) Ship has hollow shape increasing volume - Submarines rise and sink by
a) Changing density of sea water
b) Filling or emptying ballast tanks with water or air
c) Reducing weight of submarine
d) Changing mass of submarine
Answer: b) Filling or emptying ballast tanks with water or air - An iceberg floats in water because
a) Ice is heavier than water
b) Ice is less dense than water
c) Ice has more mass
d) Ice has zero density
Answer: b) Ice is less dense than water - The fraction of an iceberg submerged in water is
a) Equal to density of water
b) 0.92
c) 0.08
d) Equal to volume of water
Answer: b) 0.92 - Fish rise or sink in water by
a) Changing weight
b) Expanding and contracting swim bladder
c) Increasing fins
d) Moving faster
Answer: b) Expanding and contracting swim bladder - Balloons rise in air because
a) Weight of balloon is less than weight of air displaced
b) Balloon is small in size
c) Balloon is tied with string
d) Air pressure is more inside
Answer: a) Weight of balloon is less than weight of air displaced - The upthrust experienced by a body is independent of
a) Volume of fluid displaced
b) Density of fluid
c) Acceleration due to gravity
d) Shape of body
Answer: d) Shape of body - A body floats with 1/4th of its volume above the liquid. Relative density of body is
a) 0.25
b) 0.50
c) 0.75
d) 0.80
Answer: c) 0.75 - The centre of buoyancy lies at
a) Bottom of body
b) Top of body
c) Centre of gravity of displaced liquid
d) Centre of gravity of whole body
Answer: c) Centre of gravity of displaced liquid - The condition for flotation of a body in a fluid is
a) Density of body = Density of liquid
b) Volume of body = Volume of liquid
c) Pressure on body = Pressure of fluid
d) Upthrust = Weight of body
Answer: d) Upthrust = Weight of body - The apparent weight of floating body is
a) Zero
b) Equal to actual weight
c) Greater than actual weight
d) Equal to upthrust
Answer: a) Zero - A body weighs 60 N in air and 50 N in water. The weight of displaced water is
a) 60 N
b) 50 N
c) 10 N
d) 110 N
Answer: c) 10 N - Which liquid will provide maximum upthrust to the same body?
a) Water
b) Mercury
c) Oil
d) Alcohol
Answer: b) Mercury - Density of a body is 2 g/cm³ and density of liquid is 1 g/cm³. The body will
a) Float fully
b) Float partially
c) Sink
d) Oscillate
Answer: c) Sink - A body weighs 25 N in air and 20 N in a liquid. The relative density of the body is
a) 5
b) 25
c) 20
d) 0.8
Answer: a) 5 - Archimedes’ Principle is not applicable to
a) Liquids
b) Gases
c) Solids
d) Both liquids and gases
Answer: c) Solids - Relative density of water is taken as
a) 0
b) 1
c) 10
d) 1000
Answer: b) 1 - A body has relative density 0.6. Fraction of body submerged in water is
a) 0.4
b) 0.6
c) 0.2
d) 0.8
Answer: b) 0.6 - Unit of relative density is
a) kg/m³
b) N
c) N/m²
d) No unit
Answer: d) No unit - The experiment to verify Archimedes’ principle uses
a) Spring balance and beaker
b) Thermometer
c) Voltmeter
d) Magnet
Answer: a) Spring balance and beaker - A body displaces 50 cm³ of water. The upthrust acting on it is
a) 50 N
b) 0.5 N
c) 0.05 N
d) 0.49 N
Answer: d) 0.49 N - Buoyant force depends on
a) Volume of fluid displaced
b) Density of fluid
c) g
d) All of these
Answer: d) All of these - A cork floats in water because
a) Density of cork < Density of water
b) Density of cork > Density of water
c) Cork is heavy
d) Cork is irregular in shape
Answer: a) Density of cork < Density of water - Upthrust is maximum in
a) Oil
b) Water
c) Mercury
d) Alcohol
Answer: c) Mercury - If weight of body = upthrust, the body
a) Sinks
b) Floats inside the liquid
c) Rises up
d) Bursts
Answer: b) Floats inside the liquid - If a body floats in a liquid, then density of body / density of liquid =
a) Volume displaced / Total volume
b) Weight / Mass
c) Volume / Area
d) Upthrust / Weight
Answer: a) Volume displaced / Total volume - Which of these rises in air due to flotation principle?
a) Rocket
b) Balloon
c) Plane
d) Kite
Answer: b) Balloon - When a solid of relative density 3 is fully immersed in water, its apparent weight is
a) One-third of actual weight
b) Two-thirds of actual weight
c) Zero
d) Equal to actual weight
Answer: b) Two-thirds of actual weight - A wooden block floats on water. If the density of block is 0.8 g/cm³, the fraction of volume above water is
a) 0.2
b) 0.8
c) 0.5
d) 1.0
Answer: a) 0.2
Fill in the Blanks
- The upward force exerted by a fluid on a body immersed in it is called
a) Weight
b) Pressure
c) Upthrust
d) Force of gravity
Answer: c) Upthrust - The SI unit of upthrust is
a) g/cm³
b) N
c) N/m²
d) kg/m³
Answer: b) N - Buoyancy acts in which direction?
a) Downward
b) Horizontally
c) Upward
d) Along the weight
Answer: c) Upward - The upthrust on a body increases with
a) Increase in weight of body
b) Increase in volume submerged
c) Decrease in fluid density
d) Time of immersion
Answer: b) Increase in volume submerged - For the same volume of body, the upthrust is greater in
a) Oil
b) Water
c) Mercury
d) Kerosene
Answer: c) Mercury - The point where upthrust is considered to act is called
a) Centre of mass
b) Centre of gravity
c) Centre of buoyancy
d) Centre of pressure
Answer: c) Centre of buoyancy - A body floats in a liquid when
a) Weight > Upthrust
b) Weight < Upthrust
c) Weight = Upthrust
d) Volume = Density
Answer: c) Weight = Upthrust - A body sinks in a fluid when
a) Density of body > Density of liquid
b) Density of body < Density of liquid
c) Weight = Upthrust
d) None of these
Answer: a) Density of body > Density of liquid - The apparent loss of weight of a body immersed in liquid is equal to
a) Actual weight of body
b) Weight of displaced liquid
c) Upthrust + Weight
d) Volume of body
Answer: b) Weight of displaced liquid - Archimedes’ principle is used to determine
a) Speed
b) Pressure
c) Relative density
d) Distance
Answer: c) Relative density - According to Archimedes’ Principle, the upthrust is equal to
a) Weight of liquid displaced
b) Volume of liquid displaced
c) Density of liquid
d) Pressure in liquid
Answer: a) Weight of liquid displaced - Apparent weight of a body in a fluid is
a) Actual weight + Upthrust
b) Actual weight – Upthrust
c) Upthrust – Actual weight
d) 0 always
Answer: b) Actual weight – Upthrust - Which body experiences greater upthrust in water?
a) A small stone
b) A wooden log
c) An iron cube of same size
d) All experience same upthrust if volume submerged is same
Answer: d) All experience same upthrust if volume submerged is same - The density of water at 4°C is
a) Minimum
b) Maximum
c) Zero
d) Constant at all temperatures
Answer: b) Maximum - The SI unit of density is
a) g/cm³
b) kg/m³
c) N/m²
d) kg/m²
Answer: b) kg/m³ - Relative density has
a) SI unit same as density
b) No unit
c) Unit N/m²
d) Unit g/cm³
Answer: b) No unit - Relative density =
a) Density of substance / Density of water
b) Volume of substance / Volume of water
c) Mass / Volume
d) Weight / Upthrust
Answer: a) Density of substance / Density of water - A body of density 0.8 g/cm³ floats in water. Its relative density is
a) 0.8
b) 1.2
c) 8.0
d) 80
Answer: a) 0.8 - A solid floats when
a) Density of solid = Density of liquid
b) Density of solid < Density of liquid
c) Density of solid > Density of liquid
d) No relation with density
Answer: b) Density of solid < Density of liquid - If a body weighs 10 N in air and 6 N in water, upthrust is
a) 16 N
b) 10 N
c) 4 N
d) 6 N
Answer: c) 4 N - The principle of flotation states that a body floats when
a) Weight of liquid displaced < Weight of body
b) Weight of liquid displaced = Weight of body
c) Volume displaced = Volume of body
d) Density of body = Density of air
Answer: b) Weight of liquid displaced = Weight of body - An iron nail sinks but an iron ship floats because
a) Nail is small
b) Ship has hollow shape increasing volume
c) Ship is lighter than water
d) Nail is denser than iron
Answer: b) Ship has hollow shape increasing volume - Submarines rise and sink by
a) Changing density of sea water
b) Filling or emptying ballast tanks with water or air
c) Reducing weight of submarine
d) Changing mass of submarine
Answer: b) Filling or emptying ballast tanks with water or air - An iceberg floats in water because
a) Ice is heavier than water
b) Ice is less dense than water
c) Ice has more mass
d) Ice has zero density
Answer: b) Ice is less dense than water - The fraction of an iceberg submerged in water is
a) Equal to density of water
b) 0.92
c) 0.08
d) Equal to volume of water
Answer: b) 0.92 - Fish rise or sink in water by
a) Changing weight
b) Expanding and contracting swim bladder
c) Increasing fins
d) Moving faster
Answer: b) Expanding and contracting swim bladder - Balloons rise in air because
a) Weight of balloon is less than weight of air displaced
b) Balloon is small in size
c) Balloon is tied with string
d) Air pressure is more inside
Answer: a) Weight of balloon is less than weight of air displaced - The upthrust experienced by a body is independent of
a) Volume of fluid displaced
b) Density of fluid
c) Acceleration due to gravity
d) Shape of body
Answer: d) Shape of body - A body floats with 1/4th of its volume above the liquid. Relative density of body is
a) 0.25
b) 0.50
c) 0.75
d) 0.80
Answer: c) 0.75 - The centre of buoyancy lies at
a) Bottom of body
b) Top of body
c) Centre of gravity of displaced liquid
d) Centre of gravity of whole body
Answer: c) Centre of gravity of displaced liquid - The condition for flotation of a body in a fluid is
a) Density of body = Density of liquid
b) Volume of body = Volume of liquid
c) Pressure on body = Pressure of fluid
d) Upthrust = Weight of body
Answer: d) Upthrust = Weight of body - The apparent weight of floating body is
a) Zero
b) Equal to actual weight
c) Greater than actual weight
d) Equal to upthrust
Answer: a) Zero - A body weighs 60 N in air and 50 N in water. The weight of displaced water is
a) 60 N
b) 50 N
c) 10 N
d) 110 N
Answer: c) 10 N - Which liquid will provide maximum upthrust to the same body?
a) Water
b) Mercury
c) Oil
d) Alcohol
Answer: b) Mercury - Density of a body is 2 g/cm³ and density of liquid is 1 g/cm³. The body will
a) Float fully
b) Float partially
c) Sink
d) Oscillate
Answer: c) Sink - A body weighs 25 N in air and 20 N in a liquid. The relative density of the body is
a) 5
b) 25
c) 20
d) 0.8
Answer: a) 5 - Archimedes’ Principle is not applicable to
a) Liquids
b) Gases
c) Solids
d) Both liquids and gases
Answer: c) Solids - Relative density of water is taken as
a) 0
b) 1
c) 10
d) 1000
Answer: b) 1 - A body has relative density 0.6. Fraction of body submerged in water is
a) 0.4
b) 0.6
c) 0.2
d) 0.8
Answer: b) 0.6 - Unit of relative density is
a) kg/m³
b) N
c) N/m²
d) No unit
Answer: d) No unit - The experiment to verify Archimedes’ principle uses
a) Spring balance and beaker
b) Thermometer
c) Voltmeter
d) Magnet
Answer: a) Spring balance and beaker - A body displaces 50 cm³ of water. The upthrust acting on it is
a) 50 N
b) 0.5 N
c) 0.05 N
d) 0.49 N
Answer: d) 0.49 N - Buoyant force depends on
a) Volume of fluid displaced
b) Density of fluid
c) g
d) All of these
Answer: d) All of these - A cork floats in water because
a) Density of cork < Density of water
b) Density of cork > Density of water
c) Cork is heavy
d) Cork is irregular in shape
Answer: a) Density of cork < Density of water - Upthrust is maximum in
a) Oil
b) Water
c) Mercury
d) Alcohol
Answer: c) Mercury - If weight of body = upthrust, the body
a) Sinks
b) Floats inside the liquid
c) Rises up
d) Bursts
Answer: b) Floats inside the liquid - If a body floats in a liquid, then density of body / density of liquid =
a) Volume displaced / Total volume
b) Weight / Mass
c) Volume / Area
d) Upthrust / Weight
Answer: a) Volume displaced / Total volume - Which of these rises in air due to flotation principle?
a) Rocket
b) Balloon
c) Plane
d) Kite
Answer: b) Balloon - When a solid of relative density 3 is fully immersed in water, its apparent weight is
a) One-third of actual weight
b) Two-thirds of actual weight
c) Zero
d) Equal to actual weight
Answer: b) Two-thirds of actual weight - A wooden block floats on water. If the density of block is 0.8 g/cm³, the fraction of volume above water is
a) 0.2
b) 0.8
c) 0.5
d) 1.0
Answer: a) 0.2
Name the Following
- The upward force experienced by a body immersed in a fluid
Answer: Upthrust - The principle stating that upthrust equals the weight of displaced liquid
Answer: Archimedes’ Principle - The point where the resultant upthrust acts on a body
Answer: Centre of buoyancy - A body floats when its density is less than the fluid, this is called
Answer: Flotation - The SI unit of density
Answer: kg/m³ - The unit of upthrust
Answer: Newton - The ratio of density of a substance to the density of water
Answer: Relative density - Apparent loss of weight of a body in a liquid
Answer: Upthrust - Body with density greater than liquid sinks, this phenomenon is called
Answer: Sinking - Body with density less than liquid floats, this phenomenon is called
Answer: Floating - The experiment to verify Archimedes’ Principle uses this instrument
Answer: Spring balance - The fraction of a floating body submerged in liquid depends on
Answer: Relative density - The property of a body to experience an upward force in a fluid
Answer: Buoyancy - A hollow iron ship floats due to
Answer: Principle of Flotation - The volume of liquid displaced by a floating body
Answer: Submerged volume - The organ in fish that controls its floating
Answer: Swim bladder - The principle used to find relative density of a solid
Answer: Archimedes’ Principle - The factor that increases upthrust for the same volume
Answer: Density of liquid - Temperature at which water has maximum density
Answer: 4°C - A human body floats due to presence of
Answer: Air in lungs - A force acting opposite to weight in fluid
Answer: Upthrust - The fraction of iceberg above water depends on
Answer: Relative density - Submarines sink or float by adjusting
Answer: Ballast water - Balloons rise because the gas inside is less dense than
Answer: Air - The type of body that remains fully submerged without sinking
Answer: Neutral buoyancy body - The effect that reduces the weight of body in fluid
Answer: Upthrust - Density is defined as mass per unit
Answer: Volume - Relative density is a ________ quantity
Answer: Dimensionless - The SI unit of relative density
Answer: None - When a body is fully immersed, upthrust acts through
Answer: Centre of buoyancy - Body sinks when its density is ________ than fluid density
Answer: Greater - Body floats when its density is ________ than fluid density
Answer: Less - A solid with density equal to water ________ in water
Answer: Remains suspended - The method used to determine relative density of a liquid
Answer: Archimedes’ Principle - Floating of iron ships is an application of
Answer: Principle of Flotation - Floating of human body in water is an example of
Answer: Flotation - Rising of hot air balloons demonstrates
Answer: Principle of Flotation - Icebergs floating in sea are explained by
Answer: Principle of Flotation - Fish maintains depth using
Answer: Swim bladder - Apparent weight loss of body in liquid is equal to
Answer: Upthrust - The pressure difference on top and bottom surfaces of a submerged body causes
Answer: Upthrust - The experimental verification of Archimedes’ Principle uses this container
Answer: Overflow can - A hollow iron structure floats due to its average
Answer: Density - Relative density of water is considered as
Answer: 1 - The phenomenon when a body is completely submerged but does not sink
Answer: Neutral flotation - Density of a substance is influenced by its
Answer: Temperature - Floating of submarines is controlled by adjusting the
Answer: Volume of ballast tanks - The upward force on a body immersed in gas is called
Answer: Buoyancy - The property of liquid that determines upthrust for same volume
Answer: Density - The force that makes a body appear lighter in water
Answer: Upthrust
Answer in One Word
- What is the upward force experienced by a body immersed in a fluid called?
Answer: Upthrust - Which principle states that upthrust is equal to the weight of the displaced fluid?
Answer: Archimedes - What is the point where the upthrust acts on a body called?
Answer: Buoyancy - A body floats in a fluid if its density is ______ than the fluid.
Answer: Less - A body sinks in a fluid if its density is ______ than the fluid.
Answer: Greater - What is the SI unit of upthrust?
Answer: Newton - Mass per unit volume of a substance is called its ______.
Answer: Density - The ratio of the density of a substance to the density of water is called ______.
Answer: Relative - The apparent loss of weight of a body in a fluid is equal to its ______.
Answer: Upthrust - When a body floats, its weight is in ______ with the upthrust.
Answer: Equilibrium - Which instrument is used to verify Archimedes’ Principle experimentally?
Answer: Balance - The fraction of a floating body immersed in a fluid is called the ______.
Answer: Submerged - Which organ in fish helps it control its buoyancy?
Answer: Swimbladder - Why does a hollow ship made of iron float on water?
Answer: Volume - At what temperature does water have maximum density?
Answer: 4°C - In which direction does upthrust act on a body in a fluid?
Answer: Upward - What is a body called that remains fully submerged without sinking?
Answer: Neutral - Which liquid provides the maximum upthrust for the same volume of body?
Answer: Mercury - What is the SI unit of density?
Answer: kg/m³ - What is the unit of relative density?
Answer: None - A floating body is partially submerged due to the principle of ______.
Answer: Flotation - The force that makes a body feel lighter when immersed in a fluid is called ______.
Answer: Upthrust - Submarines rise or sink by adjusting the amount of ______ in their ballast tanks.
Answer: Ballast - Why does a balloon rise in air?
Answer: Gas - What is the approximate density of ice?
Answer: 0.92 - What fraction of an iceberg floats above water?
Answer: 0.1 - When a body floats, the weight of the body is equal to the ______ of the displaced fluid.
Answer: Weight - What is the relative density of water?
Answer: 1 - Which factor affects the density of a substance?
Answer: Temperature - What effect does upthrust have on a body in a fluid?
Answer: Lightness - A body sinks if its density is ______ than the density of the fluid.
Answer: Greater - A body floats if its density is ______ than the density of the fluid.
Answer: Less - The centre of buoyancy is the centre of ______ of the displaced liquid.
Answer: Gravity - What is the apparent weight of a fully floating body?
Answer: Zero - Which principle is used to determine the relative density of solids?
Answer: Archimedes - Which principle is used to determine the relative density of liquids?
Answer: Archimedes - The volume of fluid displaced by a floating body is called the ______.
Answer: Submerged - Floating of a human body is explained by the principle of ______.
Answer: Flotation - Icebergs float due to the principle of ______.
Answer: Flotation - Upthrust depends directly on the ______ of the fluid.
Answer: Density - The volume of a floating body submerged depends on its ______.
Answer: Relative - Fish control their depth using the ______.
Answer: Swimbladder - Hot air balloons rise due to ______.
Answer: Buoyancy - A body that is completely submerged but does not rise or sink is in ______.
Answer: Neutral - The apparent loss of weight of a body equals the ______ acting on it.
Answer: Upthrust - For the same volume of body, upthrust is determined by the ______ of the fluid.
Answer: Density - The centre of buoyancy is the centre of ______ of the displaced liquid.
Answer: Gravity - A body will sink if its density is ______ than the fluid density.
Answer: Greater - A body will float if its density is ______ than the fluid density.
Answer: Less - Upthrust depends on the acceleration due to ______.
Answer: Gravity
ICSE - Grade 9 - Physics
All Chapters
- Chapter 1 Measurement and Experimentation
- Chapter 2 Motion in one dimension
- Chapter 3 Laws of Motion
- Chapter 4 Pressure in fluids and Atmospheric pressure
- Chapter 5 Upthrust in Fluids, Archimedes’ Principle and Floatation
- Chapter 6 Heat and energy
- Chapter 7 Reflection of light
- Chapter 8 Propagation of Sound waves
- Chapter 9 Current Electricity
- Chapter 10 Magnetism
ICSE - Grade 9 - Chemistry
All Chapters
- Chapter 1 The Language of Chemistry
- Chapter 2 Chemical Changes and Reactions
- Chapter 3 Water
- Chapter 4 Atomic Structure and Chemical Bonding
- Chapter 5 The periodic table
- Chapter 6 Study of the first Element Hydrogen
- Chapter 7 Study of Gas laws
- Chapter 8 Atmospheric Pollution
ICSE - Grade 9 - Mathematics
All Chapters
- Chapter 1 Rational and Irrational Numbers
- Chapter 2 Compound Interest [Without Using Formula]
- Chapter 3 Compound Interest [Using Formula]
- Chapter 4 Expansions
- Chapter 5 Factorisation
- Chapter 6 Simultaneous Equations
- Chapter 7 Indices
- Chapter 8 Logarithms
- Chapter 9 Triangles
- Chapter 10 Isosceles Triangles
- Chapter 11 Inequalities
- Chapter 12 Midpoint and Its Converse
- Chapter 13 Pythagoras Theorem
- Chapter 14 Rectilinear Figures
- Chapter 15 Construction of Polygons
- Chapter 16 Area Theorems
- Chapter 17 Circle
- Chapter 18 Statistics
- Chapter 19 Mean and Median
- Chapter 20 Area and Perimeter of Plane Figures
- Chapter 21 Solids
- Chapter 22 Trigonometrical Ratios
- Chapter 23 Trigonometrical Ratios of Standard Angles
- Chapter 24 Solutions of Right Triangles
- Chapter 25 Complementary Angles
- Chapter 26 Coordinate Geometry
- Chapter 27 Graphical Solution
- Chapter 28 Distance Formula
ICSE - Grade 9 - Biology
All Chapters
- Chapter 1 Introducing Biology
- Chapter 2 Cell: The Unit Of Life
- Chapter 3 Tissues: Plant And Animal Tissue
- Chapter 4 The Flower
- Chapter 5 Pollination and Fertilization
- Chapter 6 Seeds: Structure and Germination
- Chapter 7 Respiration in Plants
- Chapter 8 Five Kingdom Classification
- Chapter 9 Economic Importance of Bacteria and Fungi
- Chapter 10 Nutrition
- Chapter 11 Digestive system
- Chapter 12 Skeleton: Movement and Locomotion
- Chapter 13 Skin: The Jack of all trades
- Chapter 14 The Respiratory System
- Chapter 15 Hygiene: [A key to Healthy Life]
- Chapter 16 Diseases: Cause and Control
- Chapter 17 Aids to Health
- Chapter 18 Health Organizations
- Chapter 19 Waste Generation and Management
ICSE - Grade 9 - History
All Chapters
- Chapter 1 – The Harappan Civilisation
- Chapter 2 – The Vedic Period
- Chapter 3 – Jainism and Buddhism
- Chapter 4 – The Mauryan Empire
- History — Chapter 5
The Sangam Age - Chapter 6 – The Age of the Guptas
- Chapter 7 – Medieval India — (A) The Cholas
- Chapter 8 – Medieval India — (B) The Delhi Sultanate
- Chapter 9 – Medieval India — (C) The Mughal Empire
- Chapter 10 – Medieval India — (D) Composite Culture
- Chapter 11 – The Modern Age in Europe — (A) Renaissance
- Chapter 12 – The Modern Age in Europe — (B) Reformation
- Chapter 13 – The Modern Age in Europe — (C) Industrial Revolution
ICSE - Grade 9 - Civics
All Chapters
- Chapter 1: Our Constitution
- Chapter 2: Salient Features of the Constitution — I
- Chapter 3: Salient Features of the
- Constitution — II
- Chapter 4: Elections
- Chapter 5: Local Self-Government — Rural
- Chapter 6: Local Self-Government — Urban
ICSE - Grade 9 - Geography
All Chapters
- Ch 1 – Earth as a Planet
Ch 2 – Geographic Grid: Latitudes and Longitudes
Ch 3 – Rotation and Revolution
Ch 4 – Earth’s Structure
Ch 5 – Landforms of the Earth
Ch 6 – Rocks
Ch 7 – Volcanoes
Ch 8 – Earthquakes
Ch 9 – Weathering
Ch 10 – Denudation
Ch 11 – Hydrosphere
Ch 12 – Composition and Structure of the Atmosphere
Ch 13 – Insolation
Ch 14 – Atmospheric Pressure and Winds
Ch 15 – Humidity
Ch 16 – Pollution
Ch 17 – Sources of Pollution
Ch 18 – Effects of Pollution
Ch 19 – Preventive Measures
Ch 20 – Natural Regions of the World
Find the Odd Man Out
- Upthrust, Buoyancy, Gravity, Float
Answer: Gravity
Explanation: Gravity acts downward, while the others act upward or relate to flotation. - Mercury, Water, Oil, Air
Answer: Air
Explanation: Air is a gas; the others are liquids providing upthrust. - Sink, Float, Neutral, Upthrust
Answer: Upthrust
Explanation: Upthrust is a force; the others are types of body behavior in fluid. - Archimedes, Newton, Pascal, Boyle
Answer: Newton
Explanation: Newton is a unit of force, while the others are scientists. - Submarine, Balloon, Iceberg, Stone
Answer: Stone
Explanation: Stone does not float under normal conditions; others float. - Swimbladder, Lungs, Fins, Tail
Answer: Tail
Explanation: Tail is for movement, others control buoyancy. - Upward, Downward, Vertical, Horizontal
Answer: Horizontal
Explanation: Upthrust acts vertically upward; horizontal is unrelated. - Relative density, Density, Mass, Volume
Answer: Mass
Explanation: Mass is not a ratio or density-related property. - Ice, Iron, Water, Wood
Answer: Iron
Explanation: Iron sinks in water; others can float or are less dense. - Float, Sink, Rise, Fall
Answer: Fall
Explanation: Fall is due to gravity; others relate to buoyancy. - Upthrust, Weight, Pressure, Buoyancy
Answer: Pressure
Explanation: Pressure is scalar acting in all directions; others are forces on bodies. - Balloon, Hot air, Gas, Helium
Answer: Balloon
Explanation: Balloon contains the gas; the others are types of gases. - Submerged, Floating, Sinking, Lifting
Answer: Lifting
Explanation: Lifting is not a state of body in fluid. - Density, Relative density, Volume, Force
Answer: Force
Explanation: Force is not a material property like the others. - Iceberg, Ship, Balloon, Stone
Answer: Stone
Explanation: Stone cannot float; others float due to buoyancy. - Buoyancy, Upthrust, Gravity, Flotation
Answer: Gravity
Explanation: Gravity acts downward; others act upward or describe flotation. - Air, Water, Mercury, Oil
Answer: Air
Explanation: Air is a gas, others are liquids that can exert upthrust. - Neutral, Float, Sink, Heavy
Answer: Heavy
Explanation: Heavy is an adjective; others are states of a body in fluid. - Upthrust, Centre of buoyancy, Displaced liquid, Density
Answer: Density
Explanation: Density is a property; others are related to forces and displacement. - 4°C, 0°C, 100°C, 25°C
Answer: 0°C
Explanation: 0°C is freezing point; 4°C is where water density is maximum. - Relative density, Specific gravity, Mass, Weight
Answer: Mass
Explanation: Mass is not a ratio; others relate to density comparison. - Submarine, Balloon, Fish, Stone
Answer: Stone
Explanation: Stone cannot adjust buoyancy; others can float or rise. - Water, Oil, Mercury, Ice
Answer: Ice
Explanation: Ice is solid; others are liquids. - Archimedes, Galileo, Newton, Kelvin
Answer: Kelvin
Explanation: Kelvin is a unit; others are scientists. - Balloon, Airplane, Submarine, Ship
Answer: Airplane
Explanation: Airplane does not float in fluid; others float. - Upthrust, Gravity, Weight, Friction
Answer: Friction
Explanation: Friction is a surface force; others act in fluids. - Mercury, Water, Oil, Ice
Answer: Ice
Explanation: Ice is solid, others are liquids that exert upthrust. - Float, Sink, Neutral, Jump
Answer: Jump
Explanation: Jump is an action, others are states in fluid. - Density, Mass, Volume, Force
Answer: Force
Explanation: Force is not a material property; others are related to density. - Submerged, Floating, Rising, Moving
Answer: Moving
Explanation: Moving is not a state of body in fluid. - Iron, Wood, Ice, Oil
Answer: Iron
Explanation: Iron sinks; others float due to lower density than water. - Balloon, Gas, Hot air, Steam
Answer: Balloon
Explanation: Balloon is a container, others are gases. - Upthrust, Buoyancy, Weight, Friction
Answer: Friction
Explanation: Friction is not related to fluids; others are. - Float, Sink, Slide, Neutral
Answer: Slide
Explanation: Slide is motion along a surface, not fluid behavior. - Submarine, Iceberg, Ship, Stone
Answer: Stone
Explanation: Stone cannot float, others float due to buoyancy. - Mercury, Water, Oil, Air
Answer: Air
Explanation: Air is gas; others are liquids providing upthrust. - Upthrust, Density, Volume, Gravity
Answer: Gravity
Explanation: Gravity acts downward; others relate to buoyancy and fluid properties. - Swimbladder, Lungs, Tail, Fins
Answer: Tail
Explanation: Tail is for movement; others control buoyancy. - Archimedes, Newton, Pascal, Boyle
Answer: Newton
Explanation: Newton is a unit; others are scientists. - Iceberg, Ship, Balloon, Stone
Answer: Stone
Explanation: Stone sinks; others float. - Floating, Sinking, Jumping, Neutral
Answer: Jumping
Explanation: Jumping is not a fluid state. - Upthrust, Buoyancy, Weight, Force
Answer: Force
Explanation: Force is general; others specifically relate to fluid behavior. - Water, Mercury, Oil, Air
Answer: Air
Explanation: Air is gas; others are liquids providing upthrust. - 4°C, 0°C, 25°C, 100°C
Answer: 0°C
Explanation: 0°C is freezing; 4°C is maximum water density. - Relative density, Density, Mass, Volume
Answer: Mass
Explanation: Mass is not a ratio or density-related property. - Neutral, Float, Sink, Heavy
Answer: Heavy
Explanation: Heavy is an adjective; others are fluid states. - Ice, Iron, Wood, Oil
Answer: Iron
Explanation: Iron sinks; others float. - Submarine, Balloon, Fish, Stone
Answer: Stone
Explanation: Stone cannot float or adjust buoyancy. - Centre of buoyancy, Upthrust, Displaced liquid, Mass
Answer: Mass
Explanation: Mass is not related to force or displacement. - Hot air balloon, Ship, Submarine, Stone
Answer: Stone
Explanation: Stone cannot float; others float due to buoyancy or displacement.
Match the Pair
Set 1
Column A
- Upthrust
- Archimedes’ Principle
- Centre of buoyancy
- Relative density
- Flotation
Column B (Shuffled)
A. Ratio of density of a substance to water
B. Force acting upward on a body in a fluid
C. Point where upthrust acts
D. Condition for a body to float
E. Upthrust equals weight of displaced fluid
Answers:
1 – B
2 – E
3 – C
4 – A
5 – D
Set 2
Column A
- Condition for floating
- Density
- Apparent weight
- Submerged volume
- Effect of temperature on density
Column B (Shuffled)
A. Weight of body decreases in fluid
B. Mass per unit volume
C. Increases/decreases density of water
D. Depends on relative density
E. Weight of displaced fluid equals body’s weight
Answers:
1 – E
2 – B
3 – A
4 – D
5 – C
Set 3
Column A
- Solid denser than fluid
- Solid less dense than fluid
- Ballast tank in submarine
- Hot air balloon
- Swimbladder in fish
Column B (Shuffled)
A. Helps control depth
B. Floats
C. Sinks
D. Adjusts submarine’s density
E. Rises in air
Answers:
1 – C
2 – B
3 – D
4 – E
5 – A
Set 4
Column A
- Unit of upthrust
- SI unit of density
- Unit of relative density
- Upthrust depends on
- Fraction of floating body submerged
Column B (Shuffled)
A. Newton
B. None
C. Acceleration due to gravity
D. kg/m³
E. Relative density of body
Answers:
1 – A
2 – D
3 – B
4 – C
5 – E
Set 5
Column A
- Iceberg floating
- Flotation of ship
- Balloon rising
- Fish controlling buoyancy
- Body suspended fully in fluid
Column B (Shuffled)
A. Density slightly less than water
B. Volume of enclosed air increases buoyancy
C. Less dense gas than air
D. Adjusts swimbladder
E. Neutral density
Answers:
1 – A
2 – B
3 – C
4 – D
5 – E
Set 6
Column A
- Archimedes’ experimental verification
- Condition for sinking
- Condition for floating
- Apparent loss of weight
- Centre of gravity of displaced liquid
Column B (Shuffled)
A. Equal to upthrust
B. Body heavier than displaced fluid
C. Body lighter than displaced fluid
D. Using spring balance
E. Centre of buoyancy
Answers:
1 – D
2 – B
3 – C
4 – A
5 – E
Set 7
Column A
- Water density at maximum
- Ice density
- Relative density of water
- Submarine rising
- Submarine sinking
Column B (Shuffled)
A. 0.92 g/cm³
B. 4°C
C. 1
D. Decreases ballast water
E. Increases ballast water
Answers:
1 – B
2 – A
3 – C
4 – D
5 – E
Set 8
Column A
- Upthrust increases with
- Body sinks when
- Body floats when
- Body remains neutral
- Principle used for RD of solids
Column B (Shuffled)
A. Volume submerged
B. Density less than fluid
C. Volume of fluid displaced
D. RD = ρ/ρ_water
E. Density greater than fluid
Answers:
1 – C
2 – E
3 – B
4 – A
5 – D
Set 9
Column A
- Apparent weight in liquid
- Upthrust acts in
- Icebergs floating fraction above water
- Example of relative density <1
- Example of relative density >1
Column B (Shuffled)
A. Upward
B. Iron
C. Ice
D. Less than actual weight
E. 1/10
Answers:
1 – D
2 – A
3 – E
4 – C
5 – B
Set 10
Column A
- Principle of flotation
- Displacement of fluid depends on
- Factors affecting upthrust
- Balloon rises because
- Fish floats due to
Column B (Shuffled)
A. Gas inside is lighter than air
B. Volume submerged and density
C. Volume of body, density of fluid, g
D. Upthrust balances weight
E. Swimbladder
Answers:
1 – D
2 – B
3 – C
4 – A
5 – E
Short Answer Questions
- What is upthrust?
Answer: Upthrust is the upward force exerted by a fluid on a body immersed in it. - In which direction does upthrust act?
Answer: Upthrust acts vertically upward. - State Archimedes’ Principle.
Answer: Upthrust on a body immersed in a fluid is equal to the weight of the fluid displaced by the body. - Where does the upthrust act on a body?
Answer: Upthrust acts at the centre of buoyancy. - When does a body float?
Answer: A body floats when its density is less than the density of the fluid. - When does a body sink?
Answer: A body sinks when its density is greater than the density of the fluid. - Define density.
Answer: Density is the mass per unit volume of a substance. - What is the unit of upthrust?
Answer: The SI unit of upthrust is Newton (N). - Give the unit of density.
Answer: The SI unit of density is kilogram per cubic meter (kg/m³). - What is relative density?
Answer: Relative density is the ratio of the density of a substance to the density of water. - Does relative density have a unit?
Answer: No, relative density is a dimensionless quantity. - What is the reason for upthrust?
Answer: Upthrust arises due to the pressure difference between the top and bottom surfaces of the body in fluid. - How does volume of submerged body affect upthrust?
Answer: Larger the volume of the body submerged, greater is the upthrust. - How does density of fluid affect upthrust?
Answer: Greater the density of the fluid, greater is the upthrust on the same volume. - What is apparent weight?
Answer: Apparent weight is the weight of a body in a fluid reduced by upthrust. - What is the condition for a body to remain suspended in a fluid?
Answer: A body remains suspended if its density equals the density of the fluid. - How can relative density of a solid be determined?
Answer: By measuring its loss of weight in water using Archimedes’ Principle. - How can relative density of a liquid be determined?
Answer: By using a solid of known density and applying Archimedes’ Principle. - Give an example of a body floating in water.
Answer: A piece of wood floats in water. - Give an example of a body sinking in water.
Answer: A stone sinks in water. - Why do icebergs float?
Answer: Icebergs float because the density of ice is slightly less than that of water. - Why do submarines sink or float?
Answer: Submarines adjust the volume of water in ballast tanks to change their overall density. - Why does a human body float in water?
Answer: The human body floats because lungs contain air, reducing average density. - Why does a hot air balloon rise?
Answer: A hot air balloon rises because the hot air inside is less dense than the surrounding air. - What is the centre of buoyancy?
Answer: The centre of buoyancy is the centre of gravity of the displaced fluid. - What is the relationship between upthrust and displaced fluid?
Answer: Upthrust is equal to the weight of the displaced fluid. - Does upthrust depend on the shape of the body?
Answer: No, upthrust depends only on the volume of displaced fluid. - How does temperature affect the density of water?
Answer: Density of water decreases when temperature rises above 4°C. - Why does ice float on water?
Answer: Ice floats because its density is less than that of water. - Give an example of relative density less than 1.
Answer: Wood has a relative density less than 1. - Give an example of relative density greater than 1.
Answer: Iron has a relative density greater than 1. - What is the principle of flotation?
Answer: A floating body displaces its own weight of fluid. - How is the volume of submerged part of a floating body related to densities?
Answer: Fraction submerged = Density of body / Density of fluid. - Why do fish float in water?
Answer: Fish float because their swim bladder adjusts their average density. - Why do balloons rise in air?
Answer: Balloons rise because the density of the gas inside is less than the density of air. - What happens to upthrust if a body is fully submerged?
Answer: Upthrust equals the weight of the fluid displaced by the entire body. - Why is apparent weight less in fluid than in air?
Answer: Because upthrust acts upward, reducing effective weight. - Why does mercury exert more upthrust than water for the same volume?
Answer: Because mercury has a greater density than water. - What is the SI unit of relative density?
Answer: Relative density has no unit. - What happens to a body if its density equals that of fluid?
Answer: It remains suspended at any level in the fluid. - Give an example of flotation in daily life.
Answer: Iron ships float due to their hollow structure. - How does ballast tank control depth of submarine?
Answer: Filling water increases density to sink; emptying water decreases density to float. - What is the effect of upthrust on a stone immersed in water?
Answer: It reduces the apparent weight of the stone. - What is the effect of increasing fluid density on a floating body?
Answer: Less volume of the body is submerged. - Name the property of fluid responsible for upthrust.
Answer: Pressure difference with depth in the fluid. - What is the weight of fluid displaced by a floating body equal to?
Answer: The weight of the floating body. - What is the use of Archimedes’ Principle in laboratories?
Answer: To determine density or relative density of solids and liquids. - Why does a balloon sink if air inside is cooled?
Answer: Cooling increases the density of the gas inside. - What happens to submerged volume if body density increases?
Answer: Greater volume of the body gets submerged. - Why do icebergs float mostly below water?
Answer: Because density of ice is slightly less than water, so most of its volume is submerged.
Puzzles
- I am the upward force experienced by a body in fluid. What am I?
Answer: Upthrust - I float when my density is less than water. Who am I?
Answer: Wood - I am equal to the weight of the fluid displaced by a body. What principle am I?
Answer: Archimedes’ Principle - I am the point through which upthrust acts. What am I called?
Answer: Centre of buoyancy - I sink if my density is greater than the fluid. What am I?
Answer: Stone - I have no unit but tell you whether a substance floats or sinks. What am I?
Answer: Relative density - I help a fish stay at any depth without swimming. Who am I?
Answer: Swim bladder - I float mostly submerged in water, and I am made of ice. What am I?
Answer: Iceberg - I allow a submarine to sink or rise. What am I?
Answer: Ballast tank - I am a hot object that rises in air because my density is lower than surroundings. What am I?
Answer: Hot air balloon - I act vertically upwards on a submerged body. What am I?
Answer: Upthrust - I am a ratio of density of a substance to water. What am I?
Answer: Relative density - I am a force that reduces apparent weight. What am I?
Answer: Upthrust - I float because I displace my own weight of fluid. What am I?
Answer: Floating body - I am larger when the submerged volume increases. What am I?
Answer: Upthrust - I am denser than water but can float if shaped cleverly. What am I?
Answer: Iron ship - I measure mass per unit volume. What am I?
Answer: Density - I am the reason a stone feels lighter in water. What am I?
Answer: Upthrust - I am weight in air minus loss of weight in water. What concept am I?
Answer: Relative density of solid - I help balloons rise in air. What property of air am I using?
Answer: Buoyancy - I am the principle used to find density of irregular solids. What am I?
Answer: Archimedes’ Principle - I float because I enclose air and reduce average density. What am I?
Answer: Hollow object - I am the fraction of a floating body submerged. What determines me?
Answer: Ratio of density of body to fluid - I am the SI unit of upthrust. What am I?
Answer: Newton (N) - I am dimensionless and compare density of substances. What am I?
Answer: Relative density - I increase if fluid density increases. What am I?
Answer: Upthrust - I am maximum when the body is fully submerged. What am I?
Answer: Upthrust - I help fish float without effort. What am I?
Answer: Swim bladder - I float because density of ice is less than water. What am I?
Answer: Ice - I displace fluid equal to my weight. What am I?
Answer: Floating body - I sink because my density is more than water. What am I?
Answer: Stone - I am the weight of the fluid displaced by a submerged object. What am I?
Answer: Upthrust - I am less than actual weight when measured in water. What am I?
Answer: Apparent weight - I determine whether a ship floats or sinks. What am I?
Answer: Principle of flotation - I rise when air inside me is heated. What am I?
Answer: Hot air balloon - I am submerged volume over total volume of a floating body. What ratio am I?
Answer: Fraction of submerged volume - I sink or float depending on relative density. What am I?
Answer: Body in fluid - I am the centre of gravity of displaced fluid. What am I?
Answer: Centre of buoyancy - I help in designing ships and submarines. What principle do I use?
Answer: Archimedes’ Principle - I float mostly underwater, with small part above. What am I?
Answer: Iceberg - I measure upthrust by difference in weight in air and water. What am I?
Answer: Spring balance - I float when weight = upthrust. What am I?
Answer: Floating body - I reduce apparent weight in fluid. Why?
Answer: Because upthrust acts opposite to weight - I sink when ballast tank is full. What am I?
Answer: Submarine - I float when ballast tank is empty. What am I?
Answer: Submarine - I float because I enclose large volume of air. What am I?
Answer: Ship hull - I rise when surrounding air is denser than inside. What am I?
Answer: Balloon - I displace more fluid if I am denser. What determines me?
Answer: Submerged volume - I am used to find relative density of liquids. What method do I use?
Answer: Archimedes’ Principle - I am the reason a body remains suspended in fluid. What am I?
Answer: Neutral buoyancy
Difference Between:
- Difference between Upthrust and Weight
Upthrust: The upward force experienced by a body immersed in a fluid due to pressure difference.
Weight: The downward gravitational force acting on a body due to gravity. - Difference between Density and Relative Density
Density: Mass per unit volume of a substance (kg/m³).
Relative Density: Ratio of density of a substance to the density of water; dimensionless. - Difference between Floating and Sinking Bodies
Floating Body: Density less than fluid; upthrust balances weight; partially submerged.
Sinking Body: Density greater than fluid; upthrust less than weight; completely submerged. - Difference between Centre of Buoyancy and Centre of Gravity
Centre of Buoyancy: Point through which upthrust acts; centroid of displaced fluid.
Centre of Gravity: Point through which weight acts; centroid of the body. - Difference between Archimedes’ Principle and Principle of Flotation
Archimedes’ Principle: Upthrust on a body = weight of displaced fluid.
Principle of Flotation: A floating body displaces its own weight of fluid. - Difference between Apparent Weight and True Weight
Apparent Weight: Weight of a body measured in a fluid; reduced by upthrust.
True Weight: Actual weight in air; unaffected by fluid. - Difference between Solid Relative Density and Liquid Relative Density
Solid Relative Density: Found by comparing weight in air and weight loss in water.
Liquid Relative Density: Found by comparing weight loss of a solid in water and in the liquid. - Difference between Buoyant Force and Upthrust
Buoyant Force: Another name for upthrust; can be used generally for floating and submerged bodies.
Upthrust: Specific term for upward force on a body in a fluid; measured in Newtons. - Difference between Submerged Body and Floating Body
Submerged Body: Completely inside fluid; may sink or be neutrally buoyant.
Floating Body: Partially submerged; density less than fluid; upthrust balances weight. - Difference between Mass and Weight
Mass: Quantity of matter; constant; unit kg.
Weight: Force due to gravity on mass; varies with g; unit N. - Difference between Density of Water and Density of Mercury
Density of Water: 1 g/cm³ at 4°C.
Density of Mercury: 13.6 g/cm³; denser, gives larger upthrust. - Difference between Fully Submerged and Partially Submerged Body
Fully Submerged: Entire volume in fluid; upthrust = weight only if neutrally buoyant.
Partially Submerged: Only part in fluid; floating; upthrust balances weight. - Difference between Buoyancy in Air and Buoyancy in Water
Air: Very small upthrust; negligible for most objects.
Water: Large upthrust; easily observable; supports floating bodies. - Difference between Relative Density <1 and Relative Density >1
<1: Body floats in water.
>1: Body sinks in water. - Difference between Submarine Floating and Submarine Sinking
Floating: Ballast tanks empty; density < water; upthrust ≥ weight.
Sinking: Ballast tanks filled; density > water; upthrust < weight. - Difference between Hot Air Balloon Rising and Descending
Rising: Hot air reduces balloon density; upthrust > weight.
Descending: Balloon air cools; density > surrounding air; upthrust < weight. - Difference between Ice and Iceberg
Ice: Small floating solid; may float with little submersion.
Iceberg: Large floating mass; mostly submerged; density slightly less than water. - Difference between Volume of Body and Volume of Displaced Fluid
Volume of Body: Total physical volume of object.
Volume of Displaced Fluid: Portion submerged; depends on body density and fluid. - Difference between Neutral Buoyancy and Floating
Neutral Buoyancy: Body neither sinks nor rises; density = fluid density.
Floating: Body partially submerged; density < fluid; upthrust = weight. - Difference between Experimental Verification of Archimedes’ Principle and Application
Experimental Verification: Using spring balance or measuring upthrust; proves principle.
Application: Calculating relative density, designing ships/submarines; practical use of principle.
Assertion and Reason
Instructions:
- Read both the Assertion (A) and Reason (R) carefully.
- Choose the correct option:
A. Both A and R are true, and R is the correct explanation of A
B. Both A and R are true, but R is NOT the correct explanation of A
C. A is true, R is false
D. A is false, R is true
- A: Upthrust acts on a body immersed in a fluid.
R: It is due to the pressure difference between the top and bottom of the body.
Answer: A - A: A body floats if its density is less than that of the fluid.
R: Upthrust is greater than the weight of the body.
Answer: B - A: Archimedes’ Principle states that upthrust equals the weight of the displaced fluid.
R: This principle helps in determining the relative density of solids and liquids.
Answer: A - A: The upthrust acts through the centre of buoyancy.
R: The centre of buoyancy is the centre of gravity of the displaced liquid.
Answer: A - A: A solid denser than the fluid sinks.
R: The upthrust is less than the weight of the body.
Answer: A - A: Density is mass per unit volume.
R: Density determines whether a body will float or sink.
Answer: B - A: Relative density has no unit.
R: It is a ratio of density of a substance to density of water.
Answer: A - A: Submarines float and sink by adjusting the volume of ballast water.
R: Increasing water in ballast tanks increases the overall density of the submarine.
Answer: A - A: A human body floats in water.
R: The lungs contain air which reduces the average density of the body.
Answer: A - A: Icebergs float on water.
R: The density of ice is slightly less than that of water.
Answer: A - A: Upthrust depends on the density of the fluid.
R: Greater the density of fluid, greater is the upthrust for the same volume.
Answer: A - A: Upthrust is measured in Newtons.
R: Upthrust is a type of force.
Answer: A - A: A floating body displaces its own weight of fluid.
R: According to Archimedes’ Principle, the upthrust equals the weight of the displaced fluid.
Answer: A - A: Relative density of a solid can be determined using Archimedes’ Principle.
R: Loss of weight in water equals the weight of displaced water.
Answer: A - A: Relative density of a liquid can be determined using a solid denser than water.
R: The solid floats partially in the liquid to determine its relative density.
Answer: C - A: Hot air balloons rise in air.
R: The gas inside the balloon is less dense than the surrounding air.
Answer: A - A: Water has maximum density at 4°C.
R: Ice floats because its density is less than water at 4°C.
Answer: B - A: A body remains suspended fully in fluid without sinking.
R: Its density equals the density of the fluid.
Answer: A - A: Upthrust acts vertically upwards.
R: It is caused due to difference in pressure on the top and bottom surfaces.
Answer: A - A: A body sinks if its density is greater than the fluid.
R: A body sinks if upthrust is greater than weight.
Answer: C - A: Density is an intrinsic property of matter.
R: Mass and volume of a body can vary but density remains constant.
Answer: A - A: Balloons float because of buoyant force.
R: The balloon contains gas less dense than air.
Answer: A - A: Ice floats in water.
R: Ice is heavier than water.
Answer: C - A: Flotation occurs when the weight of the body equals the upthrust.
R: This is the condition for a floating body.
Answer: A - A: Centre of buoyancy lies below the body.
R: It is the centre of gravity of displaced liquid.
Answer: A - A: Submarines sink when ballast tanks are filled with water.
R: The overall density becomes greater than water.
Answer: A - A: Upthrust increases with volume of submerged body.
R: Larger volume displaces more fluid.
Answer: A - A: Mercury exerts more upthrust than water for same volume.
R: Mercury has greater density than water.
Answer: A - A: Upthrust is a vector quantity.
R: Upthrust has both magnitude and direction.
Answer: A - A: Apparent weight of a body in liquid is less than in air.
R: Upthrust acts upward reducing effective weight.
Answer: A - A: Relative density of water is 1.
R: Water is standard reference for relative density.
Answer: A - A: Icebergs float mostly above water.
R: Ice has density slightly less than water.
Answer: B - A: Archimedes’ Principle applies only to liquids.
R: Gases exert upthrust too.
Answer: D - A: A body floats partially submerged in water.
R: Its weight equals the weight of displaced water.
Answer: A - A: Upthrust is independent of the shape of the body.
R: It depends only on the volume of fluid displaced.
Answer: A - A: Ice sinks in mercury.
R: Mercury is denser than ice.
Answer: A - A: Upthrust acts at the centre of gravity of the body.
R: It acts at the centre of buoyancy.
Answer: C - A: A stone sinks in water.
R: Its density is less than water.
Answer: C - A: Relative density has no unit.
R: Density has unit kg/m³.
Answer: A - A: Flotation is used in ships to stay afloat.
R: Ships are hollow and enclose large air volume.
Answer: A - A: Fish adjust their depth using swim bladder.
R: Swim bladder changes the average density of fish.
Answer: A - A: Hot air balloons descend when air inside is cooled.
R: Cooling increases density of gas inside.
Answer: A - A: Upthrust increases with depth in a fluid.
R: Pressure increases with depth.
Answer: B - A: Density of water decreases with temperature above 4°C.
R: Ice floats because of lower density than water.
Answer: B - A: Upthrust depends on acceleration due to gravity.
R: Weight of displaced fluid depends on g.
Answer: A - A: Floating occurs only in water.
R: Flotation can occur in any fluid.
Answer: D - A: Volume submerged of floating body depends on relative density.
R: Greater the body’s density, greater the submerged volume.
Answer: A - A: Icebergs float with most of volume submerged.
R: Density of ice is slightly less than water.
Answer: A - A: A fully submerged body experiences upthrust.
R: Upthrust depends on the volume of displaced fluid.
Answer: A - A: Upthrust is always less than the weight of the body.
R: Upthrust equals weight of displaced fluid.
Answer: C
True or False
- Upthrust acts on a body immersed in a fluid.
Answer: True - Upthrust acts downward on a submerged body.
Answer: False - Archimedes’ Principle states that upthrust is equal to the weight of the displaced fluid.
Answer: True - The centre of buoyancy is the point through which upthrust acts.
Answer: True - A body sinks if its density is greater than that of the fluid.
Answer: True - A body floats if its density is equal to the fluid.
Answer: False - Relative density has no unit.
Answer: True - Density is mass per unit volume.
Answer: True - A submarine sinks when ballast tanks are emptied.
Answer: False - Hot air balloons rise because the gas inside is denser than air.
Answer: False - Icebergs float because ice has a lower density than water.
Answer: True - Upthrust depends on the density of the fluid.
Answer: True - Upthrust is measured in kilograms.
Answer: False - Upthrust increases with the volume of the submerged body.
Answer: True - A solid denser than the fluid floats.
Answer: False - Relative density of a substance is the ratio of its density to that of water.
Answer: True - The apparent weight of a body in fluid is greater than its weight in air.
Answer: False - A body remains suspended if its density equals the density of the fluid.
Answer: True - Flotation occurs when upthrust equals the weight of the body.
Answer: True - The upthrust acts at the centre of gravity of the body.
Answer: False - A fish uses its swim bladder to control buoyancy.
Answer: True - Density of water is maximum at 4°C.
Answer: True - Ice floats mostly above water because its density is slightly more than water.
Answer: False - Mercury exerts greater upthrust than water for the same submerged volume.
Answer: True - Upthrust acts vertically upwards.
Answer: True - A body with density less than water sinks.
Answer: False - Relative density can be used to determine whether a body will float.
Answer: True - Archimedes’ Principle is only applicable to solids.
Answer: False - The volume of displaced fluid depends on the volume of the body submerged.
Answer: True - Upthrust is independent of gravity.
Answer: False - Apparent loss of weight of a body equals the upthrust.
Answer: True - Ice sinks in water.
Answer: False - A solid floating in fluid displaces its own weight of fluid.
Answer: True - Upthrust depends on the shape of the body.
Answer: False - Submarines float by controlling the amount of water in ballast tanks.
Answer: True - Hot air balloons descend when air inside is heated.
Answer: False - A body remains neutral in fluid when its density equals that of fluid.
Answer: True - Volume of fluid displaced decreases if a body floats more.
Answer: False - Relative density greater than 1 means the body will sink.
Answer: True - Density has no unit.
Answer: False - Icebergs float with most of their volume below water.
Answer: True - Upthrust is a scalar quantity.
Answer: False - Archimedes’ Principle can be used to determine the relative density of liquids.
Answer: True - Volume of the submerged part of a floating body depends on the densities of body and liquid.
Answer: True - Balloons rise in air because upthrust is greater than the weight of the balloon.
Answer: True - A floating iron ship is possible due to the principle of flotation.
Answer: True - Density of water decreases above 4°C.
Answer: True - Relative density of water is 0.92.
Answer: False - Upthrust is equal to zero for a body in vacuum.
Answer: True - Submerged volume of a floating body decreases if the density of liquid increases.
Answer: False
Long Answer Questions
- Explain what upthrust is and why it acts on a body in a fluid.
Answer: Upthrust is the upward force exerted by a fluid on a body immersed in it. It arises due to the difference in pressure at the top and bottom surfaces of the body; pressure increases with depth, so the lower surface experiences more pressure than the upper surface, resulting in an upward force called upthrust. - State and explain Archimedes’ Principle.
Answer: Archimedes’ Principle states that “a body wholly or partially immersed in a fluid experiences an upward force equal to the weight of the fluid displaced by it.” This principle explains buoyancy, flotation, and the determination of relative density of solids and liquids. - Define centre of buoyancy.
Answer: The centre of buoyancy is the point through which the upthrust acts on a body immersed in a fluid. It is the centre of gravity of the displaced fluid. - Describe the condition for a body to float in a fluid.
Answer: A body floats in a fluid if its density is less than the density of the fluid, i.e., the weight of the body is less than or equal to the weight of fluid displaced. In this case, upthrust balances the weight of the body. - Describe the condition for a body to sink in a fluid.
Answer: A body sinks in a fluid if its density is greater than that of the fluid. Here, the upthrust is less than the weight of the body, and hence the body descends to the bottom. - Define density and give its unit.
Answer: Density is the mass of a substance per unit volume, expressed as ρ = m/V. The SI unit of density is kilogram per cubic meter (kg/m³). - What is relative density? Give its unit.
Answer: Relative density is the ratio of the density of a substance to the density of water at 4°C. It is dimensionless and has no unit. - Explain how the volume of a submerged body affects upthrust.
Answer: The larger the volume of a body submerged in a fluid, the greater the amount of fluid displaced. Since upthrust equals the weight of the displaced fluid, a larger submerged volume results in greater upthrust. - Explain how the density of fluid affects upthrust.
Answer: Upthrust depends directly on the density of the fluid. For the same volume of a body submerged, a fluid with higher density exerts more upthrust because the weight of displaced fluid is greater. - What is apparent weight?
Answer: Apparent weight is the weight of a body when immersed in a fluid. It is less than its actual weight by the amount of upthrust acting on it. - Explain why a human body floats in water.
Answer: A human body floats because the lungs contain air, reducing the average density of the body. Since the density of the body becomes less than water, the upthrust balances the weight, allowing it to float. - Explain why icebergs float on water.
Answer: Ice has a slightly lower density than water (0.92 g/cm³). When placed in water, it displaces a weight of water equal to its own weight. Thus, most of the iceberg is submerged while a small portion remains above water. - Describe the principle of flotation.
Answer: The principle of flotation states that a floating body displaces its own weight of fluid. The fraction of the body submerged depends on the ratio of the body’s density to the fluid’s density: V_sub/V_body = ρ_body/ρ_fluid. - Explain how a fish controls its buoyancy.
Answer: Fish have a swim bladder, an air-filled sac. By regulating the amount of gas in the swim bladder, fish adjust their average density. Increasing gas decreases density to float, while decreasing gas increases density to sink. - Explain how a submarine sinks and rises.
Answer: Submarines have ballast tanks that can be filled with water or air. Filling tanks with water increases the submarine’s overall density, causing it to sink. Pumping air decreases density, allowing it to rise. - Describe the effect of temperature on density of water.
Answer: Water has maximum density at 4°C. Above this temperature, density decreases as temperature rises. This is why ice (0°C) floats on water. - Explain the relationship between relative density and density.
Answer: Relative density = density of substance / density of water. A substance with relative density >1 is denser than water and sinks; relative density <1 floats. - Describe the experimental verification of Archimedes’ Principle.
Answer: A solid is weighed in air and then immersed in water using a spring balance. The loss of weight equals the weight of the water displaced, confirming that upthrust equals the weight of the displaced fluid. - Explain why the upthrust acts at the centre of buoyancy.
Answer: Upthrust acts through the centre of gravity of the displaced fluid because the pressure distribution in the fluid depends on depth. The resultant upward force appears to act at this point. - Explain why the apparent weight of a stone in water is less.
Answer: The upward force (upthrust) reduces the effective weight of the stone in water, making it seem lighter than in air. - Give examples of applications of flotation.
Answer: Examples include floating of iron ships, submarines, balloons rising in air, icebergs, and fish controlling buoyancy. - Explain why hot air balloons rise.
Answer: Hot air balloons rise because the air inside is heated, reducing its density below that of surrounding air. Upthrust exceeds the weight of the balloon, lifting it upwards. - Explain why iron ships float despite iron being denser than water.
Answer: Ships have hollow structures, enclosing large volumes of air, which reduces average density below water. According to Archimedes’ Principle, upthrust balances the weight, enabling them to float. - Explain the relationship between submerged volume and densities for a floating body.
Answer: Fraction of body submerged = density of body / density of fluid. Denser bodies are more submerged to displace enough fluid to balance their weight. - Explain why a body remains suspended if its density equals that of fluid.
Answer: When body density equals fluid density, the weight of displaced fluid equals the body’s weight, resulting in neutral buoyancy; the body remains suspended anywhere in fluid. - Explain the role of upthrust in swimming.
Answer: Upthrust provides an upward force that partially counteracts the swimmer’s weight, making it easier to float and stay on water surface. - Explain how Archimedes’ Principle helps determine relative density of solids.
Answer: A solid is weighed in air and then submerged in water. Loss of weight = weight of displaced water. Relative density = weight in air / loss of weight in water. - Explain how Archimedes’ Principle helps determine relative density of liquids.
Answer: A solid of known density is weighed in air, then in the liquid. Loss of weight in liquid = weight of displaced liquid. Relative density = weight in air / loss of weight in liquid. - Explain why mercury exerts more upthrust than water.
Answer: Mercury is denser than water. For the same submerged volume, weight of displaced mercury is greater, so upthrust is larger. - Explain why the shape of a body does not affect upthrust.
Answer: Upthrust depends only on the volume of fluid displaced, not on the shape of the body. Any shape displacing the same volume experiences the same upthrust. - Explain why a balloon descends when air inside is cooled.
Answer: Cooling increases density of the air inside, reducing upthrust below the weight of the balloon, causing it to descend. - Explain the apparent loss of weight of a body in a fluid.
Answer: Apparent loss of weight = upthrust = weight of displaced fluid; the body seems lighter because the upward force partially cancels its weight. - Explain the floating of icebergs in oceans.
Answer: Icebergs float because ice density (~0.92 g/cm³) is less than water. Most of iceberg volume is submerged, displacing water equal to its weight. - Explain why a body partially submerged floats.
Answer: Only the portion submerged displaces fluid equal to the body’s weight. Upthrust balances weight, allowing it to float with part above water. - Explain why a denser fluid increases upthrust.
Answer: Greater fluid density increases weight of displaced fluid for same volume, so upthrust becomes larger. - Explain why upthrust depends on gravity.
Answer: Upthrust = weight of displaced fluid = mass × g. If g changes, weight of displaced fluid and hence upthrust changes. - Explain why a balloon rises faster in cold air.
Answer: Cold air is denser, increasing upthrust on balloon. Reduced air density inside balloon creates a larger buoyant difference, lifting it faster. - Explain why ships are designed with hollow hulls.
Answer: Hollow hulls enclose air, lowering average density below water, ensuring upthrust can balance weight for flotation. - Explain how a body’s density determines submerged volume.
Answer: More dense bodies need to displace more fluid to balance weight, resulting in a greater submerged fraction. - Explain the importance of upthrust in daily life.
Answer: Upthrust allows ships to float, balloons to rise, fish to regulate depth, and humans to swim; it is essential for flotation and buoyancy. - Explain why solid objects feel lighter in water.
Answer: Water exerts upthrust on the object, which opposes its weight, reducing the apparent weight felt. - Explain why iron floats when shaped as a boat.
Answer: Boat’s hollow structure encloses air, reducing overall density below water, enabling flotation. - Explain the difference between density and relative density.
Answer: Density is mass per unit volume with SI unit kg/m³; relative density is dimensionless ratio of substance density to water density. - Explain the role of centre of buoyancy in stability.
Answer: Centre of buoyancy ensures that upthrust acts at the correct point; if above the centre of gravity, it stabilizes floating bodies. - Explain the importance of Archimedes’ Principle in designing ships.
Answer: Ship designers calculate volume of hull to displace water weight equal to ship weight, ensuring flotation and stability. - Explain why a body partially submerged experiences upthrust less than when fully submerged.
Answer: Upthrust = weight of displaced fluid; partially submerged body displaces less fluid, so upthrust is smaller. - Explain how density of air affects hot air balloon flight.
Answer: Lower density of surrounding air reduces weight of displaced fluid (air), so balloon rises due to lower density inside. - Explain why fish can remain at any depth without swimming.
Answer: Fish adjust swim bladder to match body density with surrounding water, achieving neutral buoyancy. - Explain why ice melts slower in water than in air.
Answer: Water exerts upthrust and absorbs heat slowly; floating ice melts slower due to reduced heat transfer. - Explain why submarines surface when ballast tanks are emptied.
Answer: Emptying ballast tanks decreases overall density below water, upthrust exceeds weight, and the submarine rises.
Give Reasons
- Why does a body immersed in a fluid experience upthrust?
Answer: Because the fluid exerts pressure on all sides of the body, and pressure increases with depth, creating a net upward force. - Why does a body float when its density is less than the fluid?
Answer: Because upthrust balances the weight of the body when it displaces a volume of fluid equal to its weight. - Why does a body sink when its density is greater than the fluid?
Answer: Because the upthrust is less than the weight of the body, so it cannot remain afloat. - Why is upthrust equal to the weight of displaced fluid?
Answer: According to Archimedes’ Principle, the upward force balances the weight of the fluid displaced by the body. - Why does the upthrust act at the centre of buoyancy?
Answer: Because the resultant of pressure forces on a submerged body passes through the centre of gravity of the displaced fluid. - Why does a wooden block float in water?
Answer: Because its density is less than that of water, and the upthrust balances its weight. - Why does a stone sink in water?
Answer: Because its density is greater than that of water, so upthrust is insufficient to support its weight. - Why does a human body float in water?
Answer: Because air in the lungs reduces average density, allowing upthrust to balance weight. - Why do icebergs float with most of their volume submerged?
Answer: Because ice density is slightly less than water, so most volume must be submerged to displace enough water weight. - Why do submarines sink or rise?
Answer: By adjusting water in ballast tanks, they change overall density relative to water to sink or float. - Why does a hot air balloon rise?
Answer: Because heated air inside reduces density, so upthrust exceeds the balloon’s weight. - Why does the apparent weight of a body decrease in water?
Answer: Because upthrust acts upward, partially counteracting the weight. - Why is relative density dimensionless?
Answer: Because it is the ratio of densities, cancelling out units. - Why is the density of water maximum at 4°C?
Answer: Because water molecules are most closely packed at this temperature. - Why do fish control buoyancy with a swim bladder?
Answer: To adjust average density for floating, sinking, or remaining suspended. - Why does a body remain suspended if its density equals the fluid?
Answer: Because upthrust exactly balances weight, resulting in neutral buoyancy. - Why does upthrust increase with submerged volume?
Answer: Because a larger volume displaces more fluid, increasing the upward force. - Why does upthrust increase with fluid density?
Answer: Because denser fluid has more mass per unit volume, increasing weight of displaced fluid. - Why do ships float despite being made of iron?
Answer: Because their hollow structure encloses air, reducing average density below water. - Why does ice float on water?
Answer: Because its density is less than water, and it displaces fluid equal to its weight. - Why does a balloon sink when air inside is cooled?
Answer: Because cooling increases density, reducing upthrust below its weight. - Why does the shape of a body not affect upthrust?
Answer: Because upthrust depends only on the volume of fluid displaced, not shape. - Why does mercury exert more upthrust than water?
Answer: Because mercury has a greater density, so weight of displaced fluid is larger. - Why is upthrust essential for swimming?
Answer: Because it supports part of the swimmer’s weight, allowing flotation. - Why does a partially submerged body float?
Answer: Because the submerged portion displaces fluid equal to the body’s weight. - Why can Archimedes’ Principle be used to find relative density of solids?
Answer: By measuring weight in air and loss of weight in fluid, relative density can be calculated. - Why can Archimedes’ Principle be used to find relative density of liquids?
Answer: By comparing weight loss of a solid in water and the liquid, relative density can be determined. - Why does a body experience neutral buoyancy when density equals fluid?
Answer: Because weight of displaced fluid equals body weight, so it neither sinks nor rises. - Why does apparent weight decrease more in denser fluids?
Answer: Because upthrust is greater in denser fluids, reducing effective weight further. - Why is the centre of buoyancy important for stability?
Answer: Because upthrust acts through it, and proper positioning prevents tilting or capsizing. - Why do balloons rise faster in colder air?
Answer: Because cold air is denser, increasing buoyant force relative to balloon weight. - Why does heating air inside a balloon cause it to rise?
Answer: Heating reduces air density inside, so balloon density becomes less than surrounding air. - Why is a ship designed with a broad base?
Answer: To displace sufficient water for upthrust and provide stability. - Why does upthrust depend on gravity?
Answer: Because upthrust equals weight of displaced fluid, which is proportional to g. - Why does a floating body displace its own weight of fluid?
Answer: According to the principle of flotation, upthrust equals weight for equilibrium. - Why does increasing fluid density decrease submerged volume?
Answer: Because less volume is needed to displace enough fluid weight to balance the body. - Why does cooling water reduce upthrust slightly?
Answer: Because density decreases below 4°C, reducing weight of displaced water. - Why do hollow objects float better than solid ones?
Answer: Hollow objects enclose air, reducing average density below fluid density. - Why does a stone feel lighter in water?
Answer: Because upthrust partially counteracts its weight. - Why does upthrust act vertically upwards?
Answer: Because pressure in fluid acts perpendicular to surfaces, creating net vertical force. - Why is the fraction of submerged body larger for denser objects?
Answer: Because they must displace more fluid weight to balance their weight. - Why does ice melt slower when floating on water than on land?
Answer: Because water absorbs heat slowly, and upthrust reduces contact with warmer air. - Why does a balloon descend if cooled?
Answer: Cooling increases air density inside, reducing buoyancy below weight. - Why is upthrust zero in vacuum?
Answer: Because there is no fluid to exert pressure on the body. - Why does a fish remain at any depth without swimming?
Answer: Swim bladder adjusts density to match water, achieving neutral buoyancy. - Why does a solid of RD <1 float on water?
Answer: Because its density is less than water, allowing upthrust to balance weight. - Why does a solid of RD >1 sink in water?
Answer: Because its density is greater than water, so upthrust cannot support it. - Why does displacement of fluid depend on submerged volume?
Answer: Because weight of displaced fluid = upthrust, which is proportional to submerged volume. - Why does heating fluid affect buoyancy?
Answer: Heating reduces fluid density, decreasing weight of displaced fluid and upthrust. - Why is Archimedes’ Principle important in designing ships and submarines?
Answer: It allows calculation of volume and density needed for flotation, stability, and control of submerged objects.
Arrange the Words
Case Studies
- Case Study: A wooden block of density 0.6 g/cm³ is placed on water.
Question: Will it float or sink? Explain.
Answer: It will float because its density is less than water (1 g/cm³). Upthrust balances its weight, and only a portion of the block is submerged. - Case Study: A metal sphere of density 8 g/cm³ is dropped in water.
Question: Will it float or sink? Explain.
Answer: It will sink because its density is greater than water. Upthrust is insufficient to balance its weight. - Case Study: A fish rises to the water surface without swimming.
Question: How does it achieve this?
Answer: The fish inflates its swim bladder, reducing overall density. Upthrust equals its weight, allowing it to rise. - Case Study: An iron ship floats in a lake.
Question: How is it possible even though iron is denser than water?
Answer: The ship has a hollow hull enclosing air. Average density of ship < water, so upthrust balances its weight, enabling flotation. - Case Study: A stone weighs 10 N in air and 8 N in water.
Question: What is the upthrust on the stone?
Answer: Upthrust = Weight in air − Weight in water = 10 − 8 = 2 N. - Case Study: Ice floats in water with 90% submerged.
Question: Explain why most of it is underwater.
Answer: Ice density (0.92 g/cm³) < water density. Submerged volume fraction = 0.92. Upthrust balances the ice weight. - Case Study: A submarine fills its ballast tanks with water.
Question: What happens to the submarine?
Answer: Filling tanks increases density > water, upthrust < weight, and submarine sinks. - Case Study: The same submarine empties water from tanks.
Question: What happens now?
Answer: Density < water, upthrust > weight, so submarine rises to the surface. - Case Study: A balloon rises when air inside is heated.
Question: Why does it rise?
Answer: Heated air density decreases, making balloon density less than surrounding air. Upthrust exceeds weight, lifting it. - Case Study: A solid cube is suspended in water, neither sinking nor rising.
Question: What can you say about its density?
Answer: Its density equals water’s density. Upthrust = weight, resulting in neutral buoyancy. - Case Study: A piece of wood floats in oil (density 0.8 g/cm³).
Question: Will it float higher or lower compared to water?
Answer: Wood density ≈ 0.6 g/cm³ < oil, so fraction submerged = 0.6/0.8 = 0.75. More submerged than in water (fraction submerged 0.6). - Case Study: A body of volume 0.02 m³ is fully submerged in water.
Question: What is the upthrust on the body? (Density of water = 1000 kg/m³, g = 10 m/s²)
Answer: Upthrust = weight of displaced fluid = ρ × V × g = 1000 × 0.02 × 10 = 200 N. - Case Study: A steel cube floats in mercury.
Question: Explain why it floats despite being denser than water.
Answer: Mercury density (13.6 g/cm³) > steel density (~7.8 g/cm³). Steel density < mercury, so it floats with partial submersion. - Case Study: A solid weighs 50 N in air, 30 N in water.
Question: Calculate relative density.
Answer: Relative density = Weight in air / Loss of weight = 50 / (50−30) = 50/20 = 2.5. - Case Study: An ice cube floats on water.
Question: If it melts, what happens to water level?
Answer: Water level remains the same because ice displaces water equal to its weight. On melting, it occupies same volume as displaced water. - Case Study: A balloon is partially filled with hot air.
Question: If surrounding air cools, what happens?
Answer: Surrounding air density increases; balloon upthrust decreases relative to weight; balloon may descend. - Case Study: A cube floats in a liquid with 25% volume submerged.
Question: What is the relative density of the cube?
Answer: Relative density = Fraction submerged = 0.25. - Case Study: A ship carrying heavy cargo floats.
Question: Explain why it does not sink.
Answer: Ship hull displaces enough water weight equal to total weight (cargo + ship), upthrust balances weight. - Case Study: Iceberg has 10% above water.
Question: What is its density?
Answer: Fraction submerged = 0.9, so density of ice = 0.9 × density of water = 0.9 × 1000 = 900 kg/m³. - Case Study: A solid is fully submerged in water and upthrust is 100 N.
Question: If the same solid is placed in mercury, what happens to upthrust?
Answer: Upthrust increases because mercury density > water density.
Numericals
- A body of volume 0.01 m³ is submerged in water (density 1000 kg/m³). Calculate the upthrust. (g = 10 m/s²)
Answer: Upthrust = ρ × V × g = 1000 × 0.01 × 10 = 100 N.
Explanation: The upward force acting on a body immersed in a fluid is given by upthrust. Here, the entire volume is submerged, so upthrust = weight of displaced water = 100 N. - A metal cube of mass 2 kg and volume 0.0002 m³ is fully submerged in water. Find upthrust and determine whether it floats or sinks.
Answer: Upthrust = ρ × V × g = 1000 × 0.0002 × 10 = 2 N
Weight = mg = 2 × 10 = 20 N
Since weight > upthrust, the cube sinks.
Explanation: The upthrust is less than the weight of the cube, so it cannot float and sinks completely. - A solid weighs 50 N in air and 30 N in water. Find upthrust and relative density.
Answer: Upthrust = 50 − 30 = 20 N
Relative density = Weight in air / Loss of weight = 50 / 20 = 2.5
Explanation: Relative density indicates how many times heavier the substance is compared to water. - A wooden block of density 0.8 g/cm³ floats in water. Find the fraction submerged.
Answer: Fraction submerged = density of block / density of water = 0.8 / 1 = 0.8
Explanation: Only 80% of the block’s volume is underwater while floating because its density is less than water. - An iron cube of side 10 cm is placed in water. Density of iron = 7.8 g/cm³. Will it float?
Answer: Density of iron > water → it sinks.
Explanation: Since the material’s density is higher than water, the upthrust is insufficient to support its weight. - A body of mass 500 g and volume 400 cm³ is placed in water. Determine whether it floats.
Answer: Density = mass / volume = 500 g / 400 cm³ = 1.25 g/cm³
Since 1.25 > 1, the body sinks.
Explanation: Upthrust is less than the weight; hence the body cannot float. - A block floats in oil (density 0.9 g/cm³) with 80% submerged. Find block density.
Answer: Density of block = fraction submerged × density of fluid = 0.8 × 0.9 = 0.72 g/cm³
Explanation: The fraction submerged is proportional to relative density. - Upthrust on a fully submerged body in water is 150 N. Find volume if water density = 1000 kg/m³, g = 10 m/s².
Answer: V = Upthrust / (ρ × g) = 150 / (1000 × 10) = 0.015 m³
Explanation: Upthrust equals weight of displaced fluid, so V = 0.015 m³. - Relative density of a solid is 2. Will it float in water?
Answer: No, since relative density > 1, it sinks.
Explanation: Bodies denser than water cannot float; upthrust is insufficient. - A solid floats in water with 60% submerged. Find relative density.
Answer: Relative density = fraction submerged = 0.6
Explanation: Relative density is the ratio of body density to water; partial submersion confirms floating. - A body weighs 200 N in air and 180 N in water. Find upthrust.
Answer: Upthrust = 200 − 180 = 20 N
Explanation: The difference in weight in air and in water gives the upthrust experienced by the body. - A cube of volume 0.001 m³ and density 500 kg/m³ is placed in water. Find fraction submerged.
Answer: Fraction submerged = ρ_body / ρ_water = 500 / 1000 = 0.5
Explanation: Half of the cube’s volume is underwater to balance weight and upthrust. - A body of volume 0.05 m³ is placed in mercury (density 13,600 kg/m³). Find upthrust.
Answer: Upthrust = ρ × V × g = 13600 × 0.05 × 10 = 6800 N
Explanation: Denser fluid exerts a larger upthrust on the same volume. - A wooden block of mass 1 kg and volume 2 × 10⁻³ m³ floats in water. Find weight and upthrust.
Answer: Weight = mg = 1 × 10 = 10 N
Upthrust = weight = 10 N (floating)
Explanation: Floating condition requires upthrust = weight; fraction submerged adjusts automatically. - Ice floats with 90% submerged. Find its density if water density = 1000 kg/m³.
Answer: Density of ice = 0.9 × 1000 = 900 kg/m³
Explanation: Fraction submerged × fluid density gives the density of floating ice. - A body of mass 10 kg is submerged in water. Find upthrust if volume = 0.01 m³.
Answer: Upthrust = ρ × V × g = 1000 × 0.01 × 10 = 100 N
Weight = mg = 10 × 10 = 100 N
Explanation: Weight = upthrust, so body is neutrally buoyant. - A balloon rises when heated. Mass = 5 kg, volume = 2 m³, density of surrounding air = 1.2 kg/m³. Find net upward force.
Answer: Upthrust = ρ × V × g = 1.2 × 2 × 10 = 24 N
Weight = mg = 5 × 10 = 50 N
Explanation: If air inside balloon is heated, its density decreases. Effective upthrust > weight → balloon rises. - A submarine of volume 500 m³ and mass 400,000 kg. Does it float? (Density of water = 1000 kg/m³, g = 10 m/s²)
Answer: Upthrust = 1000 × 500 × 10 = 5,000,000 N
Weight = 400,000 × 10 = 4,000,000 N
Since upthrust > weight, the submarine floats. - Stone weighs 15 N in air, 10 N in water. Find relative density.
Answer: Relative density = 15 / (15−10) = 3
Explanation: Relative density = weight in air / loss of weight in water. - A wooden block of density 0.8 g/cm³ and volume 500 cm³ floats. Find submerged volume.
Answer: Volume submerged = fraction submerged × total volume = 0.8 × 500 = 400 cm³ - Cube of side 5 cm floats in water. Cube density = 600 kg/m³. Find fraction submerged.
Answer: Fraction submerged = 600 / 1000 = 0.6 - A body of volume 0.02 m³ displaces 18 kg of water. Find relative density if mass = 20 kg.
Answer: Relative density = mass / weight of displaced water = 20 / 18 ≈ 1.11 → sinks - Metal sphere density = 7800 kg/m³ in mercury (density 13,600 kg/m³). Will it float?
Answer: Density of sphere < mercury → partially submerged, it floats. - Body floats in oil (density 0.8 g/cm³) with 70% submerged. Find block density.
Answer: 0.7 × 0.8 = 0.56 g/cm³ - Wooden block floats in water. Weight = 50 N. Find upthrust.
Answer: Upthrust = 50 N (floating) - Ice cube mass = 0.5 kg floats. Water density = 1000 kg/m³. Find submerged volume.
Answer: Weight = 0.5 × 10 = 5 N
V_sub = Upthrust / (ρ × g) = 5 / (1000 × 10) = 0.0005 m³ - Stone weighs 100 N in air, 80 N in water. Find volume of stone.
Answer: Upthrust = 100 − 80 = 20 N
V = Upthrust / (ρ × g) = 20 / (1000 × 10) = 0.002 m³ - Wooden block floats in water with 40% submerged. Total volume = 0.02 m³. Find density of block.
Answer: ρ_block = fraction submerged × density of water = 0.4 × 1000 = 400 kg/m³ - Body mass = 12 kg floats. Upthrust = 120 N. Find g used.
Answer: Weight = mg = 12 × g = 120 → g = 10 m/s² - Balloon of volume 3 m³ rises in air (density 1.2 kg/m³). Weight = 20 N. Find upthrust.
Answer: Upthrust = 1.2 × 3 × 10 = 36 N
Net upward force = 36 − 20 = 16 N → balloon rises. - Ice cube floats, fraction submerged = 0.92. Find ice density.
Answer: 0.92 × 1000 = 920 kg/m³ - Submarine density = 1050 kg/m³, water density = 1000 kg/m³. Does it float?
Answer: Density > water → it sinks. - Cube floats with 3/4 submerged. Find relative density.
Answer: Relative density = fraction submerged = 0.75
Explanation: Relative density of a floating body equals the fraction of its volume submerged in the fluid. - Wooden block of 2 kg floats. Volume = 0.003 m³. Find upthrust.
Answer: Weight = mg = 2 × 10 = 20 N
Upthrust = weight (since floating) = 20 N
Explanation: For floating bodies, upthrust equals weight; the volume submerged adjusts automatically to balance forces. - Ice density = 900 kg/m³. Find fraction submerged in water.
Answer: Fraction submerged = density / density of water = 900 / 1000 = 0.9
Explanation: 90% of ice’s volume is underwater while floating. - Stone weighs 30 N in air, 25 N in water. Find volume of stone.
Answer: Upthrust = 30 − 25 = 5 N
Volume = Upthrust / (ρ × g) = 5 / (1000 × 10) = 0.0005 m³
Explanation: Upthrust = weight of displaced fluid; volume calculated accordingly. - Wooden cube density = 600 kg/m³, volume = 0.002 m³ floats in water. Find volume submerged.
Answer: Volume submerged = fraction submerged × total volume = 0.6 × 0.002 = 0.0012 m³ - A sphere of mass 4 kg and volume 0.002 m³ is submerged in water. Find upthrust and net force.
Answer: Upthrust = ρ × V × g = 1000 × 0.002 × 10 = 20 N
Weight = mg = 4 × 10 = 40 N
Net downward force = Weight − Upthrust = 40 − 20 = 20 N → sphere sinks - A block floats in kerosene (density 0.8 g/cm³) with 50% submerged. Find block density.
Answer: ρ_block = 0.5 × 0.8 = 0.4 g/cm³ - Ice cube floats on water. Mass = 0.2 kg. Find volume submerged.
Answer: Weight = 0.2 × 10 = 2 N
V_sub = Upthrust / (ρ × g) = 2 / (1000 × 10) = 0.0002 m³ - A wooden cylinder (density 0.75 g/cm³) floats in water. Volume submerged = 0.003 m³. Find total volume.
Answer: Fraction submerged = 0.75 / 1 = 0.75
V_total = V_sub / fraction submerged = 0.003 / 0.75 = 0.004 m³ - A body weighs 80 N in air and 50 N in water. Calculate relative density.
Answer: Relative density = Weight in air / Loss of weight = 80 / (80−50) = 80 / 30 ≈ 2.67 - A wooden block floats in water. Mass = 2 kg. Find upthrust.
Answer: Weight = 2 × 10 = 20 N
Upthrust = weight = 20 N - Stone of density 3 g/cm³ is submerged in water. Volume = 0.001 m³. Find upthrust.
Answer: Upthrust = ρ × V × g = 1000 × 0.001 × 10 = 10 N
Weight = mass × g = 3 × 0.001 × 1000 × 10 = 30 N
Net downward force = 30 − 10 = 20 N → sinks - Submarine volume = 300 m³, mass = 280,000 kg. Density of water = 1000 kg/m³. Will it float?
Answer: Upthrust = 1000 × 300 × 10 = 3,000,000 N
Weight = 280,000 × 10 = 2,800,000 N
Since upthrust > weight, it floats - A body of mass 5 kg is fully submerged in water. Volume = 0.004 m³. Calculate upthrust and net force.
Answer: Upthrust = 1000 × 0.004 × 10 = 40 N
Weight = 5 × 10 = 50 N
Net downward force = 50 − 40 = 10 N → sinks slowly - Wooden cube floats in oil (density 0.85 g/cm³) with 60% submerged. Find density of cube.
Answer: ρ_cube = fraction submerged × ρ_fluid = 0.6 × 0.85 = 0.51 g/cm³ - Iceberg floats with 90% submerged. Find density of ice if water density = 1000 kg/m³.
Answer: ρ_ice = 0.9 × 1000 = 900 kg/m³ - Body weighs 25 N in air, 20 N in water. Find volume of the body.
Answer: Upthrust = 25 − 20 = 5 N = ρ × V × g → V = 5 / (1000 × 10) = 0.0005 m³ - Wooden block mass = 1.5 kg, floats on water. Find upthrust.
Answer: Weight = mg = 1.5 × 10 = 15 N
Upthrust = 15 N (floating)
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