Questions & Answers
CBSE - Grade - 8
Subject: Science
Chapter - 08 - Force and Pressure
Types of Questions
MCQ
- Which of the following is not a contact force?
(a) Muscular force
(b) Friction
(c) Magnetic force
(d) Force of push
(c) Magnetic force
- Force can change the __________ of an object.
(a) shape
(b) speed
(c) direction
(d) all of these
(d) all of these
- Which of these can be used to describe force?
(a) Smell
(b) Push or Pull
(c) Colour
(d) Temperature
(b) Push or Pull
- What happens when equal and opposite forces are applied on an object?
(a) Object starts moving
(b) Object breaks
(c) Net force becomes zero
(d) Object changes shape
(c) Net force becomes zero
- Which of the following is a non-contact force?
(a) Friction
(b) Muscular force
(c) Electrostatic force
(d) Normal force
(c) Electrostatic force
- The SI unit of force is:
(a) Kilogram
(b) Newton
(c) Pascal
(d) Joule
(b) Newton
- Force applied over a unit area is called:
(a) Pressure
(b) Work
(c) Energy
(d) Force per second
(a) Pressure
- What is the unit of pressure?
(a) Newton
(b) Newton/metre
(c) Newton/metre²
(d) Newton/second
(c) Newton/metre²
- Which type of force is used to open a door?
(a) Magnetic
(b) Gravitational
(c) Muscular
(d) Electrostatic
(c) Muscular
- Which of these can reduce pressure on a surface?
(a) Reduce area
(b) Increase area
(c) Increase force
(d) Use a sharp object
(b) Increase area
- Which force opposes motion?
(a) Magnetic
(b) Friction
(c) Gravitational
(d) Electrostatic
(b) Friction
- The force exerted by the Earth on all objects is called:
(a) Electrostatic force
(b) Friction
(c) Magnetic force
(d) Gravitational force
(d) Gravitational force
- Which one of these is a contact force?
(a) Gravitational
(b) Electrostatic
(c) Friction
(d) Magnetic
(c) Friction
- When a rubber ball is pressed, it changes its:
(a) Colour
(b) Shape
(c) Mass
(d) Density
(b) Shape
- Force has:
(a) Only direction
(b) Only magnitude
(c) Both magnitude and direction
(d) No physical quantity
(c) Both magnitude and direction
- A moving object slows down due to:
(a) Gravity
(b) Magnetism
(c) Friction
(d) Muscular force
(c) Friction
- Air exerts:
(a) No pressure
(b) Pressure only downwards
(c) Pressure in all directions
(d) Pressure only upwards
(c) Pressure in all directions
- Which of the following increases pressure?
(a) Decrease in force
(b) Increase in area
(c) Increase in force and decrease in area
(d) Decrease in both area and force
(c) Increase in force and decrease in area
- Which of these objects uses atmospheric pressure?
(a) Balloon
(b) Dropper
(c) Syringe
(d) All of these
(d) All of these
- A porter’s turban reduces:
(a) Force
(b) Pressure
(c) Mass
(d) Weight
(b) Pressure
- Which of the following does not exert pressure?
(a) Solid
(b) Liquid
(c) Gas
(d) None of these
(d) None of these
- A rubber sucker sticks to a surface due to:
(a) Electrostatic force
(b) Friction
(c) Atmospheric pressure
(d) Gravity
(c) Atmospheric pressure
- When force is applied on an object and it moves, work is:
(a) Not done
(b) Done
(c) Negative
(d) Friction
(b) Done
- Who discovered atmospheric pressure using two hemispheres?
(a) Galileo
(b) Newton
(c) Otto von Guericke
(d) Einstein
(c) Otto von Guericke
- The force of gravity always acts:
(a) Upwards
(b) Downwards
(c) Sideways
(d) Circularly
(b) Downwards
- Electrostatic force is strongest between:
(a) Like charges
(b) Unlike charges
(c) Neutral and charged bodies
(d) None
(b) Unlike charges
- Which part of a nail creates more pressure?
(a) Head
(b) Pointed end
(c) Side
(d) None
(b) Pointed end
- Which type of force is used when stretching a spring?
(a) Friction
(b) Gravitational
(c) Muscular
(d) Magnetic
(c) Muscular
- The shape of a balloon changes when it is inflated because of:
(a) Gravity
(b) Force of pull
(c) Air pressure
(d) Friction
(c) Air pressure
- Which of the following is true?
(a) All forces are contact forces
(b) Magnetic force is a contact force
(c) Electrostatic force is non-contact
(d) Friction is a non-contact force
(c) Electrostatic force is non-contact
- The pressure exerted by a liquid increases with:
(a) Decrease in depth
(b) Increase in depth
(c) Constant depth
(d) Decrease in area
(b) Increase in depth
- The effect of force depends on:
(a) Only mass
(b) Only area
(c) Magnitude and direction
(d) Shape of object
(c) Magnitude and direction
- Friction occurs when:
(a) Objects are in contact
(b) Objects are far apart
(c) One is magnetic
(d) None of these
(a) Objects are in contact
- A charged plastic straw attracts small pieces of paper due to:
(a) Friction
(b) Magnetic force
(c) Electrostatic force
(d) Gravity
(c) Electrostatic force
- Water flows downhill due to:
(a) Air pressure
(b) Gravity
(c) Magnetic force
(d) Friction
(b) Gravity
- Which force helps to stop a moving bicycle?
(a) Electrostatic
(b) Magnetic
(c) Friction
(d) Gravitational
(c) Friction
- Pressure is inversely proportional to:
(a) Force
(b) Area
(c) Weight
(d) Mass
(b) Area
- Which of the following forces can act without touching?
(a) Friction
(b) Magnetic
(c) Muscular
(d) Applied force
(b) Magnetic
- Which of these forces can attract and repel?
(a) Gravity
(b) Magnetic
(c) Muscular
(d) Friction
(b) Magnetic
- A ball changes direction after hitting a wall due to:
(a) Air
(b) Pressure
(c) Force
(d) Magnetism
(c) Force
- The area in the pressure formula must be:
(a) Circular
(b) Unit area
(c) Random
(d) Unmeasured
(b) Unit area
- Force can never:
(a) Change shape
(b) Change speed
(c) Change temperature
(d) Change direction
(c) Change temperature
- What is required to apply a force on a body?
(a) Distance
(b) Interaction
(c) Speed
(d) Heat
(b) Interaction
- A falling object is pulled by:
(a) Air
(b) Magnet
(c) Gravity
(d) Friction
(c) Gravity
- Increase in pressure can be achieved by:
(a) Decreasing area
(b) Increasing area
(c) Using friction
(d) Reducing speed
(a) Decreasing area
- Water exerts pressure on:
(a) Only top surface
(b) Only bottom
(c) Bottom and sides
(d) Air
(c) Bottom and sides
- Tools like knives and pins have:
(a) Large surface area
(b) No force
(c) Sharp edges
(d) Rounded tips
(c) Sharp edges
- The direction of friction is always:
(a) Same as motion
(b) Opposite to motion
(c) Upwards
(d) Downwards
(b) Opposite to motion
- Which of the following uses a non-contact force?
(a) Drawing water
(b) Lifting a bag
(c) Using a bar magnet
(d) Pushing a trolley
(c) Using a bar magnet
- Atmospheric pressure is caused by:
(a) Water flow
(b) Force of air above us
(c) Gravitational pull of Moon
(d) Friction in atmosphere
(b) Force of air above us
Fill in the Blanks
- A force is a __________ or a pull.
push - Force arises due to __________ between two objects.
interaction - The SI unit of force is __________.
newton - Force can change the __________ of an object.
shape - Force has both magnitude and __________.
direction - A moving object can be stopped by applying __________.
force - A force that acts only when two objects are in contact is called a __________ force.
contact - Muscular force is a type of __________ force.
contact - The force that opposes motion is called __________.
friction - Friction is a __________ force.
contact - A force that can act without physical contact is called a __________ force.
non-contact - The force of attraction by Earth on all objects is called __________.
gravitational force - The force exerted by a magnet is known as __________ force.
magnetic - The force between charged objects is called __________ force.
electrostatic - A force may cause a change in the __________ of motion of an object.
state - If the net force on an object is zero, the object will __________.
not move - Pressure is defined as force per unit __________.
area - The SI unit of pressure is __________.
newton per square metre - 1 newton per square metre is also called __________.
pascal - If the area decreases, pressure __________.
increases - If the area increases, pressure __________.
decreases - A sharp knife cuts better because it applies more __________.
pressure - Broad straps are used in bags to reduce __________ on the shoulder.
pressure - Liquids exert pressure on the __________ and walls of the container.
bottom - As the depth of a liquid increases, the pressure __________.
increases - Gases exert pressure in __________ directions.
all - Air pressure is also known as __________ pressure.
atmospheric - The envelop of air surrounding the Earth is called the __________.
atmosphere - A balloon inflates because air inside it exerts __________.
pressure - The force that holds us to the surface of the Earth is called __________.
gravity - Force can cause a stationary object to __________.
move - In tug of war, the team that pulls with greater force __________.
wins - Like poles of magnets __________ each other.
repel - Unlike poles of magnets __________ each other.
attract - A moving object slows down due to __________.
friction - Pressure is inversely proportional to __________.
area - Water in a pipe creates pressure due to its __________.
height - Air escaping from a balloon is due to __________ pressure.
internal air - The instrument used to demonstrate atmospheric pressure is a __________.
sucker - A porter’s cloth pad increases area and hence reduces __________.
pressure - Otto von Guericke demonstrated atmospheric pressure using __________.
hemispheres - The pressure of air decreases with __________ from the Earth’s surface.
height - Electrostatic force can act on a __________ object.
charged - Force acting on an object may change its __________.
speed - A charged body can __________ an uncharged object.
attract - A magnet can attract objects made of __________.
iron - A spring changes its shape due to applied __________.
force - A nail can penetrate wood due to high __________ at its tip.
pressure - The direction of friction is always __________ to the motion.
opposite - The shape of a balloon changes when inflated due to __________ pressure.
air
Name the Following
- Name the quantity that is a push or a pull.
Force - Name the unit used to measure force.
Newton - Name the force that opposes motion between surfaces.
Friction - Name the force exerted by muscles.
Muscular force - Name the type of force that does not require contact.
Non-contact force - Name the force that pulls objects towards the Earth.
Gravitational force - Name the invisible envelope of air around the Earth.
Atmosphere - Name the force with which air presses on all objects.
Atmospheric pressure - Name the force exerted by magnets.
Magnetic force - Name the force between charged bodies.
Electrostatic force - Name the force that can change the shape of an object.
Force - Name the device used to show atmospheric pressure using suction.
Rubber sucker - Name the unit of pressure in SI system.
Pascal - Name the physical quantity defined as force per unit area.
Pressure - Name the force applied by animals like camels or bullocks.
Muscular force - Name the German scientist who demonstrated air pressure using hemispheres.
Otto von Guericke - Name the property of liquids that allows them to exert pressure.
Weight of the liquid column - Name the force responsible for attraction between iron and magnet.
Magnetic force - Name the type of poles of magnets that attract each other.
Unlike poles - Name the direction in which the force of gravity acts.
Downward - Name the force responsible for movement of a boat when rowing stops.
Friction - Name the force which can act even at a distance.
Non-contact force - Name the force that helps inflate a bicycle tyre.
Air pressure - Name the type of force applied when opening a drawer.
Muscular force - Name the direction in which frictional force acts.
Opposite to the direction of motion - Name the quantity that describes both speed and direction.
State of motion - Name the factor that increases pressure when it is reduced.
Area - Name the quantity which balances atmospheric pressure inside our body.
Internal body pressure - Name the force that helps to pick up a comb rubbed with paper.
Electrostatic force - Name the type of force applied when we kick a football.
Muscular force - Name the force responsible for water flowing down a slope.
Gravitational force - Name the shape change in dough when force is applied.
Flattening or deformation - Name the kind of contact needed for muscular force to act.
Physical contact - Name the force responsible for a balloon changing shape when inflated.
Air pressure - Name the type of force that acts in tug-of-war.
Muscular force - Name the part of a knife that produces more pressure.
Edge or tip - Name the direction in which liquid pressure acts at a point.
All directions - Name the force that helps a magnet to attract iron pins.
Magnetic force - Name the effect of force that results in a cricket ball changing direction.
Change in motion - Name the type of force responsible for pulling water up with a bucket.
Muscular force - Name the action that increases pressure on the floor while wearing high heels.
Decrease in area of contact - Name the object that works on the principle of atmospheric pressure to draw water.
Dropper - Name the common force that helps objects fall freely.
Gravity - Name the type of force used to write with a pen.
Muscular force - Name the factor that increases pressure when force increases.
Force - Name the material which gets attracted towards magnets.
Iron - Name the natural force that helps raindrops fall to the ground.
Gravitational force - Name the scientific term for a body at zero speed.
Rest - Name the type of change that occurs when a force changes the speed of an object.
Change in state of motion - Name the property of air that allows it to exert pressure on walls of a container.
Compressibility
Answer in One Word
- What is a push or a pull called?
Force - Which force slows down a moving object?
Friction - Which force pulls objects toward the Earth?
Gravity - Which force is exerted by our muscles?
Muscular - What is the SI unit of force?
Newton - Which force does not require contact?
Non-contact - What is the force acting per unit area called?
Pressure - What is the SI unit of pressure?
Pascal - Which force is responsible for the attraction between magnets and iron?
Magnetic - Which force arises due to charged objects?
Electrostatic - What is the direction of gravitational force?
Downward - What is the force that acts opposite to motion?
Friction - What surrounds the Earth and exerts pressure?
Atmosphere - Which force allows a balloon to inflate?
Air pressure - Who demonstrated atmospheric pressure using hemispheres?
Guericke - Which pole of a magnet repels the same pole?
Like - What happens to pressure when area decreases?
Increases - What happens to pressure when area increases?
Decreases - What force helps lift a bucket from a well?
Muscular - What is the quantity with both magnitude and direction?
Vector - What do you call the change in speed or direction of an object?
Motion - Which type of force requires physical contact?
Contact - What is the pressure inside our body that balances atmospheric pressure?
Internal - What instrument sticks to surfaces using atmospheric pressure?
Sucker - What happens to a balloon’s shape when inflated?
Changes - What kind of force is gravity?
Non-contact - Which force is responsible for rowing a boat?
Muscular - What force opposes motion between two surfaces?
Friction - What causes an object to fall when dropped?
Gravity - What property of liquids allows them to exert pressure?
Weight - What is the shape of a magnet’s field around it?
Invisible - What increases pressure for a given force?
Decrease in area - Which part of a knife causes more pressure?
Tip - What is the unit of gravitational force?
Newton - What causes hair to attract paper after combing?
Electrostatics - What surrounds the Earth up to many kilometers?
Atmosphere - What is the force acting on the base of a container filled with water?
Liquid pressure - Which physical quantity opposes weight in the body?
Pressure - What is the action of pulling a cart called?
Force - Which force helps a child to slide down a slope?
Gravitational - What does a rubber band change when stretched?
Shape - What is another term for zero motion?
Rest - What force helps a balloon to rise when air is blown into it?
Air pressure - Which kind of force is felt between opposite electric charges?
Attractive - What force do animals like oxen use to pull carts?
Muscular - What change occurs in the direction of motion due to force?
Deflection - Which force always acts against the direction of movement?
Friction - What type of poles in magnets attract?
Unlike - What quantity is calculated by force divided by area?
Pressure - What is the nature of gravitational force?
Attractive
ICSE - Grade 9 - Physics
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- Chapter 1 Measurement and Experimentation
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- Chapter 3 Laws of Motion
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- Chapter 9 Triangles
- Chapter 10 Isosceles Triangles
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- 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
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- Chapter 22 Trigonometrical Ratios
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- Chapter 24 Solutions of Right Triangles
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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
- Muscular force, Friction, Magnetic force, Push
Magnetic force
Explanation: All others are contact forces; magnetic is non-contact. - Pressure, Force, Area, Length
Length
Explanation: Not related to force or pressure calculations. - Gravity, Electrostatic force, Magnetic force, Friction
Friction
Explanation: Friction is a contact force; others are non-contact forces. - Magnet, Electrostatics, Comb, Muscle
Muscle
Explanation: All others relate to non-contact forces; muscle is contact. - Pulling, Pushing, Resting, Lifting
Resting
Explanation: All others involve application of force; resting does not. - Pressure, Newton, Pascal, Newton/metre²
Newton
Explanation: Others are units of pressure; Newton is unit of force. - Spring, Rubber band, Balloon, Iron
Iron
Explanation: Others change shape when force is applied; iron does not easily. - Magnet, Iron, Plastic, Steel
Plastic
Explanation: Not attracted by magnets; others are magnetic materials. - Boat, Car, Cycle, Magnet
Magnet
Explanation: All others are vehicles moved by muscular force; magnet is not. - Hammering, Cutting, Melting, Twisting
Melting
Explanation: All others involve force; melting is a physical change due to heat. - Comb, Straw, Magnet, Oxygen
Oxygen
Explanation: Not involved in force-related interactions; others can exert/experience force. - Attraction, Repulsion, Friction, Reflection
Reflection
Explanation: Not a force; others are types/effects of forces. - Newton, Joule, Pascal, Newton/metre²
Joule
Explanation: Joule is a unit of energy; others relate to force or pressure. - Push, Pull, Pressure, Mass
Mass
Explanation: Mass is not a force or effect of force. - Gravity, Magnetism, Buoyancy, Friction
Friction
Explanation: Friction is a contact force; others are non-contact or fluid forces. - Electrostatic, Magnetic, Muscular, Gravitational
Muscular
Explanation: Only muscular is a contact force. - Sharp knife, Nail, Needle, Hammer
Hammer
Explanation: All others apply high pressure via small area; hammer spreads force over larger area. - Blood pressure, Atmospheric pressure, Liquid pressure, Normal force
Normal force
Explanation: Not a type of pressure; others are. - Air, Water, Iron, Mercury
Iron
Explanation: Not a fluid; others are. - Balloon, Tyre, Bottle, Box
Box
Explanation: Others can be inflated with air; box cannot. - Comb rubbed with cloth, Magnet, Balloon, Pencil
Pencil
Explanation: Does not exert any force; others can. - Sucker, Dropper, Syringe, Mirror
Mirror
Explanation: Does not work on pressure; others do. - Push, Pull, Bend, Float
Float
Explanation: Not a force or its effect. - Apple falling, Raindrop falling, Book falling, Kite flying
Kite flying
Explanation: Others fall due to gravity; kite rises due to air. - Tug-of-war, Lifting a bag, Rowing a boat, Cooling a liquid
Cooling a liquid
Explanation: No force involved; others require force. - Horse, Ox, Camel, Magnet
Magnet
Explanation: Animals apply muscular force; magnet does not. - Atmosphere, Water, Glass, Mercury
Glass
Explanation: Not a fluid; others are. - Friction, Magnetism, Gravity, Electrostatics
Friction
Explanation: Only contact force; others are non-contact. - Hemispheres, Air, Pressure, Fire
Fire
Explanation: Not related to atmospheric pressure; others are. - Solid, Liquid, Gas, Energy
Energy
Explanation: Not a state of matter. - Water column, Depth, Height, Temperature
Temperature
Explanation: Others affect liquid pressure; temperature does not directly. - Flowing water, Wind, Moving ball, Burning candle
Burning candle
Explanation: Others involve motion and forces; burning is chemical change. - Boat stopping, Car slowing, Ball rolling, Magnet attracting
Magnet attracting
Explanation: Not due to friction; others are. - Gravitational force, Weight, Earth’s pull, Light
Light
Explanation: Not a force or effect of gravity. - Balloon, Syringe, Mirror, Dropper
Mirror
Explanation: Not used to demonstrate air pressure. - Force, Friction, Magnetism, Combustion
Combustion
Explanation: Not a type of force. - Iron, Nickel, Cobalt, Copper
Copper
Explanation: Not strongly magnetic; others are. - Sucker, Barometer, Thermometer, Syringe
Thermometer
Explanation: Measures temperature, not pressure. - Friction, Electrostatics, Magnetism, Osmosis
Osmosis
Explanation: Biological process; others involve force. - Balloon, Comb, Magnet, String
String
Explanation: Cannot exert force without contact; others can. - Comb, Balloon, Plastic ruler, Rock
Rock
Explanation: Cannot exert electrostatic force. - Tyre, Balloon, Jar, Hammer
Hammer
Explanation: Not inflated by air; others are. - Hammer, Knife, Nail, Eraser
Eraser
Explanation: Not used for applying high pressure via pointed edge. - Weight, Pressure, Speed, Force
Speed
Explanation: Scalar quantity; others are related to forces. - Horse, Donkey, Bullock, Magnet
Magnet
Explanation: Others use muscular force for pulling loads. - Gravitational, Magnetic, Frictional, Electrostatic
Frictional
Explanation: Only contact force; others are non-contact. - Pascal, Newton, Kilogram, Joule
Kilogram
Explanation: Unit of mass; others are derived units. - Dropper, Syringe, Balloon, Spoon
Spoon
Explanation: Not used to demonstrate air pressure. - Tyre, Pump, Comb, Stone
Stone
Explanation: Cannot show air or electrostatic pressure effects. - Newton, Pressure, Area, Comb
Comb
Explanation: Not a physical quantity; others are.
Match the Pair
Set 1: Match the following
Column A
- Force
- Friction
- Gravity
- Muscular force
- Pressure
Column B
a. Force by Earth
b. Push or Pull
c. Contact force due to rubbing
d. Force per unit area
e. Applied by body parts
Correct Answers:
1 → b
2 → c
3 → a
4 → e
5 → d
Set 2: Match the following
Column A
- Magnet
- Electrostatic force
- Balloon inflation
- Comb rubbed on hair
- Repulsion
Column B
a. Magnetic poles
b. Charged object attracts paper
c. Non-contact force
d. Effect of air pressure
e. Attracts iron objects
Correct Answers:
1 → e
2 → c
3 → d
4 → b
5 → a
Set 3: Match the following
Column A
- Contact force
- Non-contact force
- Gravitational force
- Magnetic force
- Frictional force
Column B
a. Present between rubbing surfaces
b. Acts at a distance
c. Type of non-contact force
d. Requires physical touch
e. Used in attracting metals
Correct Answers:
1 → d
2 → b
3 → c
4 → e
5 → a
Set 4: Match the following
Column A
- Pascal
- Newton
- Area
- Pressure
- Force
Column B
a. SI unit of pressure
b. SI unit of force
c. Measured in square metre
d. Force per unit area
e. Causes motion/change
Correct Answers:
1 → a
2 → b
3 → c
4 → d
5 → e
Set 5: Match the following
Column A
- Knife edge
- Broad belt
- Balloon
- Dropper
- Inflated tyre
Column B
a. Increases air pressure
b. Demonstrates air pressure
c. Applies pressure to cut
d. Reduces pressure on shoulder
e. Expands due to inner pressure
Correct Answers:
1 → c
2 → d
3 → e
4 → b
5 → a
Set 6: Match the following
Column A
- Otto von Guericke
- Comb attracts paper
- Spoon
- Inflated balloon
- Hemispheres
Column B
a. Not an air pressure device
b. Demonstrates atmospheric pressure
c. Electrostatic force
d. Air pressure from inside
e. Scientist who demonstrated pressure
Correct Answers:
1 → e
2 → c
3 → a
4 → d
5 → b
Set 7: Match the following
Column A
- Pulling a cart
- Tug of war
- Lifting a load
- Pressing a sponge
- Turning a doorknob
Column B
a. Change in shape
b. Muscular force
c. Rotational motion
d. Competing forces
e. Contact force
Correct Answers:
1 → b
2 → d
3 → e
4 → a
5 → c
Set 8: Match the following
Column A
- Air
- Water
- Gravity
- Electrostatics
- Magnetism
Column B
a. Attracts paper bits
b. Pulls things down
c. Exerts pressure on walls
d. Applies pressure in containers
e. Acts on iron materials
Correct Answers:
1 → d
2 → c
3 → b
4 → a
5 → e
Set 9: Match the following
Column A
- Newton per square metre
- Falling apple
- Moving cycle
- Magnet and iron
- Rubbing hands
Column B
a. Shows magnetic force
b. Produces friction
c. SI unit of pressure
d. Example of gravity
e. Affected by friction
Correct Answers:
1 → c
2 → d
3 → e
4 → a
5 → b
Set 10: Match the following
Column A
- Balloon bursts
- Knife penetrates easily
- Shoes with flat soles
- Air presses walls
- Greater height of water
Column B
a. More pressure at depth
b. Reduces pressure
c. High inner pressure
d. Increases pressure
e. Force by gas molecules
Correct Answers:
1 → c
2 → d
3 → b
4 → e
5 → a
Short Answer Questions
- What is force?
Force is a push or a pull that can change the state of motion or shape of an object. - What is the SI unit of force?
The SI unit of force is Newton (N). - What is pressure?
Pressure is the force acting per unit area. - What is the SI unit of pressure?
The SI unit of pressure is Pascal (Pa). - What type of force is friction?
Friction is a contact force. - Name one non-contact force.
Gravitational force is a non-contact force. - What kind of force is applied while kicking a ball?
Muscular force is applied while kicking a ball. - What is the direction of gravitational force?
Gravitational force always acts downward toward the Earth. - What causes a falling object to accelerate towards the ground?
Gravitational force causes it to accelerate. - What type of force is magnetic force?
Magnetic force is a non-contact force. - What is the effect of force on the shape of an object?
Force can change the shape of an object. - What is the relation between pressure and area?
Pressure is inversely proportional to area. - Why does a sharp knife cut better?
Because it applies more pressure over a smaller area. - What happens when you rub a comb on dry hair?
The comb gets electrically charged and attracts paper pieces. - Which force helps us walk without slipping?
Frictional force helps us walk. - What is the direction of frictional force?
Frictional force acts opposite to the direction of motion. - Name a device that works on atmospheric pressure.
A syringe works on atmospheric pressure. - Why do we slip on a wet floor?
Because friction is reduced on wet surfaces. - What force is used to lift a heavy box?
Muscular force is used. - What type of force is electrostatic force?
Electrostatic force is a non-contact force. - Why do astronauts float in space?
Because there is negligible gravity in space. - What is the cause of pressure in liquids?
The weight of the liquid causes pressure. - Why does pressure increase with depth in water?
Because more water exerts force at greater depths. - What is the unit of pressure when force is in Newton and area in m²?
Pascal (Pa) is the unit. - What is the effect of friction on moving objects?
Friction opposes and slows down motion. - What happens to pressure when force is increased?
Pressure increases if area remains the same. - Why are school bags made with broad straps?
To reduce pressure on shoulders by increasing area. - What kind of force is used in rowing a boat?
Muscular force is used. - Name a natural non-contact force.
Gravity is a natural non-contact force. - What kind of force is exerted by a stretched rubber band?
Elastic force is exerted. - What causes a balloon to burst if overinflated?
High internal air pressure causes it to burst. - Why do soles of shoes wear out?
Because of continuous friction with the ground. - What helps a magnet to attract iron objects?
Magnetic force helps in attraction. - What does friction produce when objects rub against each other?
Friction produces heat. - Why do we apply oil to machine parts?
To reduce friction. - What is the effect of force on a resting object?
Force can bring a resting object into motion. - Why is pressure high at a sharp tip?
Because area is small, increasing pressure. - What force helps in writing on paper?
Friction between pen and paper helps. - What kind of force is required to twist a wet cloth?
Muscular force is required. - Why does a ball stop rolling on the ground?
Due to friction between the ball and ground. - What causes a liquid to rise in a syringe?
Atmospheric pressure causes it. - What type of force is used to open a door?
Muscular force is used. - Why do we fall backward when a bus suddenly starts?
Due to inertia of rest. - Why are high heels uncomfortable on soft floors?
They exert more pressure due to small contact area. - What does a vacuum do inside a rubber sucker?
Creates low pressure to hold it tightly. - Why is water stored in tanks at heights?
To use pressure of water due to gravity. - What change does force bring in a moving object?
It can change its speed or direction. - What happens when opposite poles of magnets come close?
They attract each other. - Why do we use lubricants?
To reduce friction. - What is the net force on an object when two equal and opposite forces act on it?
The net force is zero.
Puzzles
- I pull everything towards me, but no one can see me. I keep you grounded. What am I?
Gravitational force - I’m invisible, I oppose your motion, and I make walking possible. What am I?
Friction - I can crush a can, move water up a straw, and even burst a balloon. I’m all around you. What am I?
Air pressure - I help you light a match, but I also wear out your shoes. Who am I?
Friction - I act from a distance and attract iron, but I’m not a person. What force am I?
Magnetic force - What kind of force would you use to squeeze a lemon?
Muscular force - Which force allows a plastic straw to draw liquid upwards?
Atmospheric pressure - I’m the result of force divided by area. What physical quantity am I?
Pressure - You’re using me when you rub your hands together to keep warm. What am I?
Friction - What happens to pressure if the area is doubled but force remains the same?
It becomes half - I can be attractive or repulsive, and I only work on certain materials. What am I?
Magnetic force - You fill me with air, and I expand. What causes my shape to change?
Air pressure - I act without touching. I’m created when you comb your hair and attract paper bits. What am I?
Electrostatic force - What force is responsible for the apple falling from a tree?
Gravity - Why does a pencil fall when dropped from a table?
Gravitational pull - If a force does not change an object’s motion, what kind of forces are acting on it?
Balanced forces - I’m used to lift heavy weights by pushing liquids in machines. What principle is this?
Hydraulic pressure - Which force slows down a bicycle when brakes are applied?
Friction - A balloon sticks to a wall after being rubbed. Which force causes this?
Electrostatic force - Which unit is used to measure force?
Newton - If you apply more force on the same area, what happens to the pressure?
It increases - A small nail enters wood more easily than a large-headed nail. Why?
Higher pressure due to smaller area - Two people push a box from opposite sides with equal force. What happens?
The box does not move - A ball stops after rolling for some time. Why?
Frictional force acts against motion - What force acts when you stretch a rubber band and release it?
Elastic force - You push a door and it opens. What causes the door to move?
Applied force - Which force can act through air, walls, and vacuum?
Magnetic force - A dropper can suck in liquid. Which force helps it?
Atmospheric pressure - A soccer ball is kicked and it changes direction. What is the cause?
Unbalanced force - If two forces act in the same direction, what happens to net force?
It increases - You rub a balloon on your hair, and it sticks to a wall. What force is responsible?
Electrostatic force - What happens to friction when surface is smoothened?
It decreases - A gas cylinder is filled tightly. What causes it to be pressurized?
Gas molecules exerting pressure - What force must be overcome to move a book on a table?
Static friction - A flat shoe or a stiletto? Which causes more pressure on the floor?
Stiletto - A match lights up when struck. Which force causes it?
Friction - When you press a sponge, it changes shape. Which effect of force is this?
Change in shape - What force is responsible for holding satellites in orbit?
Gravitational force - The pressure of air at sea level is more than on a mountain. Why?
Air is denser at sea level - Why can’t we drink through a straw with a hole?
Air pressure cannot act properly - You rub your palms fast and they feel warm. Why?
Friction produces heat - Why is it difficult to walk on a marble floor with wet feet?
Reduced friction - Why do people slip more often on ice than on sand?
Ice has less friction - I’m a force, I act when you throw a ball upwards and it slows down. What am I?
Gravitational force - Why does a balloon inflate when air is blown into it?
Air exerts pressure on the walls - Why are trucks provided with large number of tyres?
To distribute weight and reduce pressure - Why does a straw collapse when you suck all the air out of it?
Atmospheric pressure crushes it - Why does a sucker stick better on smooth surfaces than rough ones?
Smooth surfaces allow better vacuum seal - What causes your ear to pop when you climb a mountain quickly?
Sudden change in air pressure - Why does a parachute open during skydiving?
To increase air resistance and reduce fall speed
Difference Between:
- Contact Force vs Non-Contact Force
- Contact force requires physical contact between objects.
- Non-contact force acts without direct contact.
- Examples of contact forces: friction, muscular force.
- Examples of non-contact forces: magnetic, gravitational, electrostatic.
- Balanced Forces vs Unbalanced Forces
- Balanced forces do not change the state of motion.
- Unbalanced forces cause acceleration or change in motion.
- Balanced forces are equal and opposite.
- Unbalanced forces are unequal and may act in the same or opposite directions.
- Force vs Pressure
- Force is a push or pull on an object.
- Pressure is force applied per unit area.
- Force is measured in Newtons.
- Pressure is measured in Pascals.
- Frictional Force vs Muscular Force
- Frictional force resists motion between surfaces.
- Muscular force is exerted by muscles.
- Friction is an external resisting force.
- Muscular force is applied by living organisms.
- Gravitational Force vs Magnetic Force
- Gravitational force acts between all masses.
- Magnetic force acts on magnetic materials.
- Gravity is always attractive.
- Magnetic force can be attractive or repulsive.
- Solid Pressure vs Liquid Pressure
- Solid pressure depends on force and contact area.
- Liquid pressure depends on depth and density.
- Solid pressure is directional.
- Liquid pressure acts in all directions.
- Friction vs Lubrication
- Friction opposes motion.
- Lubrication reduces friction.
- Friction causes wear and tear.
- Lubrication protects surfaces and eases motion.
- Static Friction vs Sliding Friction
- Static friction acts on stationary objects.
- Sliding friction acts on moving surfaces.
- Static friction is usually greater.
- Sliding friction is comparatively less.
- Pressure in Liquids vs Pressure in Gases
- Liquid pressure increases with depth.
- Gas pressure depends on compression.
- Liquids are incompressible.
- Gases are compressible.
- Magnetic Force vs Electrostatic Force
- Magnetic force acts on magnetic materials.
- Electrostatic force acts on charged objects.
- Magnetic force is due to moving charges.
- Electrostatic force is due to static charges.
- Rolling Friction vs Sliding Friction
- Rolling friction occurs when an object rolls.
- Sliding friction occurs when it slides.
- Rolling friction is lesser.
- Sliding friction is greater.
- Force Applied by Hand vs Force by Machine
- Hand force is muscular.
- Machine force is mechanical.
- Hand force depends on strength.
- Machine force can be large with less effort.
- Increased Area vs Decreased Area (Effect on Pressure)
- Increased area reduces pressure.
- Decreased area increases pressure.
- Pressure is inversely proportional to area.
- Smaller area = higher pressure for same force.
- Air Pressure vs Water Pressure
- Air pressure comes from atmospheric air.
- Water pressure is due to water’s weight.
- Air is compressible, water is not.
- Air pressure decreases with height; water pressure increases with depth.
- Friction on Rough Surface vs Smooth Surface
- Rough surface has more friction.
- Smooth surface has less friction.
- Roughness increases interlocking.
- Smoothness reduces resistance.
- Force Can Start Motion vs Force Can Stop Motion
- Force applied on rest object starts motion.
- Force applied on moving object can stop it.
- Both are effects of force.
- Muscular Force vs Mechanical Force
- Muscular force is biological.
- Mechanical force is by machines.
- Muscular force is limited.
- Mechanical force is powerful.
- Friction in Solids vs Friction in Fluids
- Friction in solids is surface resistance.
- In fluids, it’s called drag.
- Solids have contact friction.
- Fluids exert resistance throughout motion.
- Friction is Useful vs Friction is Harmful
- Useful in walking, gripping, writing.
- Harmful as it causes wear and energy loss.
- Controlled friction is desired.
- High Pressure Area vs Low Pressure Area (in Balloon)
- High pressure inside a balloon makes it expand.
- Low pressure outside allows suction.
- Pressure difference helps in movement of fluids.
Assertion and Reason
Answer options used:
- (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, but R is false
- (D) A is false, but R is true
- A: Force is a push or pull.
R: Force has magnitude and direction.
(B) Both A and R are true, but R is not the correct explanation of A - A: Friction is a non-contact force.
R: Friction arises when two surfaces are in contact.
(D) A is false, but R is true - A: Muscular force is a contact force.
R: It requires physical contact between objects.
(A) Both A and R are true, and R is the correct explanation of A - A: Electrostatic force is a contact force.
R: It acts when charged objects touch each other.
(D) A is false, but R is true - A: Magnetic force can attract and repel.
R: Like poles of magnets attract each other.
(C) A is true, but R is false - A: A magnet attracts plastic and wood.
R: Magnetic force acts on all materials.
(D) A is false, but R is true - A: Pressure is the force applied on a unit area.
R: Pressure is directly proportional to the area.
(C) A is true, but R is false - A: A sharp knife cuts better than a blunt one.
R: Sharp edges apply more pressure on a smaller area.
(A) Both A and R are true, and R is the correct explanation of A - A: A balloon inflates when air is filled in it.
R: Air exerts pressure on the walls of the balloon.
(A) Both A and R are true, and R is the correct explanation of A - A: Water in a tank exerts pressure only downward.
R: Pressure in a liquid acts in all directions at a given depth.
(D) A is false, but R is true - A: Friction helps stop a moving object.
R: Friction acts opposite to the direction of motion.
(A) Both A and R are true, and R is the correct explanation of A - A: Gravitational force is a contact force.
R: It pulls objects towards the Earth.
(C) A is false, but R is true - A: A comb attracts paper pieces after rubbing.
R: Rubbing charges the comb with static electricity.
(A) Both A and R are true, and R is the correct explanation of A - A: Liquids do not exert pressure.
R: Liquids have no weight.
(D) A is false, but R is true - A: Pressure increases as area decreases.
R: Pressure is inversely proportional to area.
(A) Both A and R are true, and R is the correct explanation of A - A: Electrostatic force requires contact.
R: Charged bodies attract or repel without touching.
(D) A is false, but R is true - A: Magnetic force is a non-contact force.
R: It acts at a distance on magnetic materials.
(A) Both A and R are true, and R is the correct explanation of A - A: Gravity helps us stand on the surface of the Earth.
R: Gravity pulls everything toward the center of the Earth.
(A) Both A and R are true, and R is the correct explanation of A - A: Pressure is measured in Newton.
R: Pascal is the SI unit of pressure.
(D) A is false, but R is true - A: The shape of a rubber band does not change with force.
R: Force can change the shape of soft objects.
(C) A is false, but R is true - A: Magnets can attract plastic and paper.
R: Magnetic force acts only on magnetic materials.
(D) A is false, but R is true - A: A car moving on road experiences friction.
R: Friction occurs between car tyres and road.
(A) Both A and R are true, and R is the correct explanation of A - A: Friction helps in walking.
R: It prevents slipping.
(A) Both A and R are true, and R is the correct explanation of A - A: A body in motion will always keep moving.
R: There is no force in motion.
(C) A is true, but R is false - A: The gravitational force of the Moon is greater than Earth’s.
R: The Moon is smaller than the Earth.
(D) A is false, but R is true - A: Pressure is calculated by dividing area by force.
R: Pressure increases with increase in area.
(D) A is false, but R is true - A: Fluids exert pressure in all directions.
R: Particles in fluids can move freely.
(A) Both A and R are true, and R is the correct explanation of A - A: When we stop rowing a boat, it continues moving.
R: There is no friction in water.
(C) A is true, but R is false - A: A bar magnet attracts all metals.
R: Magnetic force acts on all substances.
(C) A is true, but R is false - A: Gravity acts only on Earth.
R: Other planets have no gravity.
(C) A is false, but R is false - A: Atmospheric pressure can be felt on our body.
R: It is balanced by the pressure of fluids inside our body.
(A) Both A and R are true, and R is the correct explanation of A - A: A balloon bursts when overinflated.
R: The internal air pressure becomes too high.
(A) Both A and R are true, and R is the correct explanation of A - A: Non-contact forces can never repel.
R: Magnetic and electrostatic forces only attract.
(D) A is false, but R is false - A: A person walking applies muscular force.
R: Movement of muscles generates force.
(A) Both A and R are true, and R is the correct explanation of A - A: We can lift objects using gravitational force.
R: Gravity always pulls objects downward.
(C) A is false, but R is true - A: A heavy object exerts less pressure on the floor.
R: Pressure increases when weight increases.
(C) A is false, but R is true - A: Friction helps in writing with a pen.
R: Friction between paper and pen allows ink to settle.
(A) Both A and R are true, and R is the correct explanation of A - A: A blunt knife cuts better than a sharp one.
R: Blunt knives apply more pressure.
(D) A is false, but R is false - A: Water exerts pressure on the sides of a container.
R: Pressure in liquids acts in all directions.
(A) Both A and R are true, and R is the correct explanation of A - A: An inflated balloon contracts in a vacuum.
R: Atmospheric pressure keeps it expanded.
(A) Both A and R are true, and R is the correct explanation of A - A: A force can change the direction of motion.
R: Direction is a part of state of motion.
(A) Both A and R are true, and R is the correct explanation of A - A: Syringes do not work without air pressure.
R: Atmospheric pressure helps push liquid inside.
(A) Both A and R are true, and R is the correct explanation of A - A: Friction can be reduced by polishing surfaces.
R: Smooth surfaces offer less resistance to motion.
(A) Both A and R are true, and R is the correct explanation of A - A: Magnetic force only exists in man-made magnets.
R: Natural magnets also exist in nature.
(D) A is false, but R is true - A: A rolling ball eventually stops on its own.
R: Friction between the ball and floor slows it down.
(A) Both A and R are true, and R is the correct explanation of A - A: More area leads to more pressure.
R: Pressure is directly proportional to area.
(C) A is false, but R is false - A: Friction can wear out machine parts.
R: Friction causes heat and erosion over time.
(A) Both A and R are true, and R is the correct explanation of A - A: Only liquids exert pressure.
R: Gases do not have mass.
(D) A is false, but R is false - A: Contact forces can act from a distance.
R: Friction is a non-contact force.
(D) A is false, but R is false - A: Pressure can be increased by increasing force.
R: Pressure is directly proportional to force.
(A) Both A and R are true, and R is the correct explanation of A
True or False
- Force can change the shape of an object.
True - Friction is a non-contact force.
False - The SI unit of force is joule.
False - Magnetic force acts only when in contact.
False - Gravity pulls objects toward the Earth.
True - Force can only change the direction of motion but not its speed.
False - Electrostatic force is a contact force.
False - Force has both magnitude and direction.
True - Pressure is force acting per unit area.
True - The SI unit of pressure is Pascal.
True - Increasing the area of contact increases the pressure.
False - A sharp knife applies more pressure than a blunt knife.
True - Muscular force is a non-contact force.
False - Air does not exert pressure.
False - Water exerts pressure on the walls of its container.
True - A magnet can attract plastic.
False - Gravitational force is a contact force.
False - Friction helps us to walk.
True - A balloon inflates due to gravity.
False - Like poles of magnets repel each other.
True - Atmospheric pressure cannot be felt by our body.
False - Non-contact forces can act without touching the object.
True - Pressure decreases with increase in force if area remains same.
False - Electrostatic force acts between charged bodies.
True - A moving object always requires continuous force to keep it moving.
False - The force of friction acts in the direction of motion.
False - Pressure is inversely proportional to the area.
True - Magnetic force acts on all materials.
False - Dropper works on atmospheric pressure.
True - Air has no weight, so it cannot exert pressure.
False - A balloon changes shape when inflated because of air pressure.
True - Comb attracts paper pieces due to electrostatic force.
True - Gravity is only present on Earth.
False - More depth in water means more pressure.
True - A force can only bring stationary objects into motion.
False - Pressure is measured in newtons.
False - Friction always slows down motion.
True - Magnetic force can act through air.
True - A magnet always repels iron.
False - Friction can cause wear and tear in machines.
True - Muscular force can only be applied by humans.
False - Electrostatic force and magnetic force are both contact forces.
False - Water pressure is the same at all depths.
False - Air pressure acts only in the upward direction.
False - Pressure is not affected by area.
False - Friction helps in writing with a pen.
True - The Earth’s gravity pulls the Moon.
True - A rubber sucker sticks due to atmospheric pressure.
True - A comb loses its charge over time.
True - Friction increases with polishing.
False
Long Answer Questions
- Define force. What are its effects on an object?
Force is a push or pull upon an object resulting from its interaction with another object. The effects of force include: (i) changing the speed of an object, (ii) changing the direction of motion, (iii) changing the shape or size of an object, and (iv) bringing an object to rest or setting it in motion. - What is the difference between contact and non-contact forces? Give examples.
Contact forces require physical contact to act, such as muscular force and friction. Non-contact forces act from a distance without physical contact, like gravitational force, magnetic force, and electrostatic force. - Describe how a magnet exerts force and classify the type of force it applies.
A magnet exerts a force of attraction or repulsion on certain materials, especially iron. This magnetic force can act through air, without direct contact, hence it is a non-contact force. - Explain the importance of friction in daily life.
Friction is essential for walking, writing, driving vehicles, lighting matchsticks, and holding objects. Without friction, objects would continue sliding, making controlled motion impossible. - What is pressure? Derive the formula and explain the relationship between pressure, force, and area.
Pressure is defined as the force applied per unit area. The formula is Pressure = Force / Area. Pressure increases with force and decreases with increase in area, showing an inverse relation with area. - Why are porters advised to use broad belts for carrying loads?
Broad belts increase the area over which the weight is distributed, reducing the pressure on shoulders. This makes it more comfortable and prevents injury. - Why do sharp knives cut better than blunt ones?
Sharp knives have a smaller contact area, and hence, apply greater pressure with the same force. This allows them to cut objects more efficiently than blunt knives. - What is atmospheric pressure? Describe one experiment that proves its existence.
Atmospheric pressure is the force exerted by the air in the atmosphere on the surface of the Earth. Otto von Guericke’s Magdeburg hemispheres experiment showed that the atmospheric pressure is strong enough to hold two hemispheres tightly together even when several horses tried to pull them apart. - What is gravitational force? State its effects on objects.
Gravitational force is the force of attraction between two objects with mass. It pulls objects towards the center of the Earth and is responsible for the fall of objects, ocean tides, and the Earth’s orbit around the Sun. - Describe muscular force and its applications.
Muscular force is the force applied using body muscles. It is a contact force and is used in activities like lifting, pushing, pulling, running, and holding objects. - Explain how pressure is exerted in liquids.
Liquids exert pressure in all directions. This is because liquid particles transmit force equally in every direction. Pressure increases with depth due to the weight of the liquid above. - Why do dams have thicker walls at the bottom?
Pressure increases with depth in a liquid. Therefore, the bottom of a dam experiences greater pressure and needs thicker walls to withstand the force of water. - What is electrostatic force? Give two real-life examples.
Electrostatic force is the force between electrically charged objects. Examples: (i) A charged comb attracts tiny paper bits, (ii) A rubbed balloon sticks to a wall. - How does friction affect motion?
Friction opposes motion between two surfaces in contact. It slows down or stops moving objects and helps in starting motion as well, such as walking or rolling a ball. - Why does a balloon burst when overfilled with air?
As air is filled, pressure increases inside the balloon. When internal air pressure exceeds the balloon’s elastic limit, it bursts. - What are the factors affecting friction?
Friction depends on (i) the nature of the surfaces in contact (smooth or rough), and (ii) the force pressing the two surfaces together. - How do lubricants help reduce friction?
Lubricants form a thin film between surfaces, reducing direct contact and therefore reducing friction. This makes motion smoother and prevents wear and tear. - Explain how a rubber sucker works.
When a sucker is pressed against a smooth surface, air is expelled. The pressure inside becomes lower than atmospheric pressure outside, and atmospheric pressure holds the sucker tightly to the surface. - How does pressure vary with depth in a liquid?
Pressure increases with depth due to the weight of the liquid column above. The deeper you go, the more liquid is above, resulting in more force on the lower layers. - What is the role of friction in sports?
Friction provides grip between shoes and ground, helps in controlling the ball, and allows players to stop, turn, or accelerate effectively. - Describe an experiment to demonstrate liquid pressure.
Take a bottle with holes at different heights. Fill it with water. Water comes out with more force from the bottom hole, showing pressure increases with depth. - Why do we feel heavier when carrying water-filled balloons than air-filled ones?
Water is denser and heavier than air. Thus, balloons filled with water exert more downward force (weight), making them feel heavier. - How do astronauts experience weightlessness?
Astronauts in orbit are in free fall under gravity, with the spacecraft. Since both fall together, there is no normal reaction force, hence they feel weightless. - Explain how atmospheric pressure affects our daily life.
Atmospheric pressure allows us to drink with a straw, use droppers, syringes, vacuum cups, and also protects our bodies by balancing internal pressure. - State two harmful effects of friction.
(i) It causes wear and tear of machinery, (ii) It generates heat, leading to energy loss. - Why do tyres of racing bikes have special designs?
To balance between reduced friction for speed and enough grip for safety during turns and braking. - What are balanced and unbalanced forces?
Balanced forces cancel each other and do not change motion. Unbalanced forces have a net effect and cause acceleration or deceleration. - How can you prove that air exerts pressure?
A crushed can experiment shows that atmospheric pressure outside can crush a can when internal pressure is reduced. - How does pressure help in injecting medicine with a syringe?
Pulling the plunger reduces pressure inside the syringe, allowing atmospheric pressure to push the liquid medicine into the syringe. - Why does a balloon shrink when placed in a refrigerator?
Cold air lowers internal pressure and temperature, reducing the volume and shrinking the balloon. - Explain how pressure in gases can be dangerous.
If gas containers are overfilled or heated, internal pressure can rise, possibly causing an explosion if not handled properly. - How is pressure important in hydraulic brakes?
Brakes apply force through fluid pressure, transmitting equal force to all brake pads, providing efficient and safe stopping. - What are the three main types of contact forces?
(i) Muscular force, (ii) Frictional force, (iii) Normal force. - Describe the types of non-contact forces.
(i) Gravitational force: attraction by Earth, (ii) Magnetic force: acts on magnetic materials, (iii) Electrostatic force: between charged bodies. - Explain why it is easier to cut vegetables with a sharp knife.
A sharp knife has less area at the edge, increasing pressure and making cutting easier. - What causes a ball thrown upward to stop and fall back?
Gravitational force opposes its motion, slows it down, stops it, and pulls it back down. - How does surface texture affect friction?
Rough surfaces have more friction due to interlocking irregularities; smooth surfaces reduce friction. - How does a parachute work using air pressure?
A parachute increases surface area, increasing air resistance (drag), which slows down the fall due to opposing pressure. - What precautions are taken to reduce friction in machines?
Using lubricants, ball bearings, and smooth surfaces helps reduce friction. - Why is it difficult to walk on ice?
Ice has low friction, so the grip is reduced, making walking difficult. - How does liquid pressure affect deep-sea divers?
They face high pressure at greater depths, so they use pressure-resistant suits to protect themselves. - Why are drawing pins pointed?
To apply high pressure on a small area, making it easier to push into surfaces. - Why do some objects float in water while others sink?
Objects float if their weight is less than the upthrust (buoyant force); otherwise, they sink. - How can you reduce friction in your daily life?
By using oil in door hinges, polishing surfaces, or using wheels on luggage. - What is the role of force in changing the state of motion?
Force can accelerate, decelerate, stop, or change the direction of an object’s motion. - Why do tyres have treads?
Treads increase friction, providing better grip on the road and preventing slipping. - How does gravity affect water flow?
Gravity pulls water downward, allowing rivers to flow and enabling water supply systems to work. - Describe how a matchstick lights due to friction.
Rubbing the matchstick head against the rough surface produces heat due to friction, igniting the chemicals. - Why is it easier to roll a suitcase with wheels?
Wheels reduce contact area and rolling friction is less than sliding friction, making it easier to move. - Why do mountaineers carry oxygen cylinders?
At high altitudes, atmospheric pressure and oxygen levels are low, so they carry oxygen to breathe properly.
Give Reasons
- Give reason: A sharp knife cuts better than a blunt one.
Because a sharp knife has a smaller area at the edge, applying more pressure for the same force, making cutting easier. - Give reason: Friction helps in walking.
Because friction between the ground and our feet prevents slipping and provides grip to move forward. - Give reason: We slip on a wet floor.
Because water reduces friction between our feet and the floor. - Give reason: A balloon bursts when overfilled.
Because the internal air pressure exceeds the elastic limit of the balloon material. - Give reason: Porters use broad belts for carrying luggage.
Because broad belts reduce pressure by increasing the area over which the weight is distributed. - Give reason: Friction produces heat.
Because rubbing surfaces convert mechanical energy into heat energy due to resistance. - Give reason: Water flows downwards from a tap.
Because of gravitational force acting on the water. - Give reason: A comb rubbed on dry hair attracts bits of paper.
Because rubbing the comb generates static electricity that creates an electrostatic force. - Give reason: It is difficult to move a box on a rough surface.
Because rough surfaces increase friction, resisting motion. - Give reason: A rubber sucker sticks to a surface.
Because air is expelled, creating low pressure inside, and atmospheric pressure holds it in place. - Give reason: Dams have thicker walls at the bottom.
Because pressure increases with depth and thicker walls can withstand higher pressure. - Give reason: Tyres have treads.
Because treads increase friction and provide better grip on the road. - Give reason: Lubricants are used in machines.
Because lubricants reduce friction and prevent wear and tear. - Give reason: We are able to write on paper with a pen.
Because of friction between the tip of the pen and paper. - Give reason: Water pressure is more at greater depths.
Because of the increased weight of the water column above. - Give reason: Ball bearings are used in machines.
Because they reduce rolling friction and allow smooth movement. - Give reason: It is easier to roll an object than to slide it.
Because rolling friction is less than sliding friction. - Give reason: We use parachutes while jumping from aircrafts.
Because parachutes increase air resistance and reduce the speed of descent. - Give reason: Astronauts feel weightless in space.
Because they are in free fall, and no normal force is acting on them. - Give reason: Drawing pins have pointed tips.
Because pointed tips concentrate force on a small area, increasing pressure for easy penetration. - Give reason: A syringe draws liquid when plunger is pulled.
Because pulling creates low pressure inside, and atmospheric pressure pushes liquid into it. - Give reason: It is difficult to walk on ice.
Because ice is smooth and has very low friction. - Give reason: Pressure is more with narrow straps.
Because a smaller area increases pressure for the same force. - Give reason: A bicycle slows down when brakes are applied.
Because friction between the brake pads and wheels opposes motion. - Give reason: Magnetic force can act from a distance.
Because it is a non-contact force that doesn’t need physical contact. - Give reason: People use rubber shoes during rainy season.
Because rubber provides better grip by increasing friction. - Give reason: Liquids exert pressure in all directions.
Because liquid molecules are free to move and transmit force equally in all directions. - Give reason: Comb attracts paper even without touching.
Because it develops electrostatic force which is a non-contact force. - Give reason: Broad tyres are used in tractors.
Because broad tyres distribute weight over a larger area and reduce pressure on soft soil. - Give reason: A balloon shrinks in the refrigerator.
Because cooling reduces internal air pressure, causing contraction. - Give reason: Pressure is more on the feet of a standing person than a lying one.
Because standing reduces contact area, increasing pressure on the ground. - Give reason: Athletes wear shoes with spikes.
Because spikes increase friction and prevent slipping during running. - Give reason: Gravity keeps the Moon in orbit.
Because Earth’s gravitational force pulls the Moon towards it, keeping it in orbit. - Give reason: Ball stops rolling after some time.
Because friction between the ball and surface opposes its motion. - Give reason: Fluids exert pressure on the container walls.
Because their particles are in constant motion and apply force in all directions. - Give reason: It is difficult to press a thumbtack on a wooden table with the head.
Because the large area of the head reduces pressure for the same applied force. - Give reason: Electrostatic forces can attract neutral objects.
Because charged objects induce opposite charge in nearby neutral objects. - Give reason: The air pressure inside a tyre supports the vehicle’s weight.
Because compressed air inside the tyre exerts outward pressure, balancing the weight. - Give reason: Spacecrafts need shielding from high pressure during re-entry.
Because atmospheric pressure increases rapidly during descent at high speeds. - Give reason: Force can start or stop motion.
Because force changes the state of motion of an object. - Give reason: We feel atmospheric pressure but don’t collapse under it.
Because internal body fluids exert equal pressure outward, balancing it. - Give reason: More pressure is exerted by a person wearing heels than flats.
Because heels have less contact area, increasing pressure. - Give reason: Syringe works even when turned upside down.
Because it depends on pressure difference, not gravity. - Give reason: Hydraulics use liquid to transmit force.
Because liquids are incompressible and transmit pressure equally in all directions. - Give reason: Wearing gloves helps in carrying hot vessels.
Because gloves reduce heat transfer and provide grip by increasing friction. - Give reason: Friction is considered both useful and harmful.
Because it helps in movement but also causes wear, tear, and heat generation. - Give reason: Cars have streamlined shape.
Because it reduces air resistance, increasing speed and fuel efficiency. - Give reason: Force can change the direction of motion.
Because applying a force at an angle changes the object’s path. - Give reason: We can’t drink juice with a straw if the top is open.
Because atmospheric pressure won’t act without suction, and liquid won’t rise. - Give reason: A thick mattress exerts less pressure than a thin one of the same weight.
Because a thick mattress has more area in contact, reducing pressure.
Arrange the Words
Case Studies
- Case Study 1:
Ravi was trying to push a heavy table but it didn’t move. His friend Amit came and applied force in the same direction, and the table started moving.
What kind of forces were initially acting and what changed?
Initially, Ravi’s force was insufficient (unbalanced). With Amit’s additional force in the same direction, the net force increased, causing motion. - Case Study 2:
Asha observed that her pen writes well on paper but slips on glass. She wondered why.
What is the reason for this difference?
Friction between pen and paper is sufficient for writing; glass has low friction, so the pen slips. - Case Study 3:
Kiran filled a plastic bottle with water, closed it tightly, and squeezed it. The bottle bulged out slightly.
Why did this happen?
Water pressure increased inside the closed bottle, pushing against its walls. - Case Study 4:
Sameer noticed that a rubber sucker sticks better on glass than on a wall.
Why does the sucker stick more effectively on glass?
Glass is smooth and allows better air-tight suction, increasing pressure difference. - Case Study 5:
A boy standing on sand with flat shoes sinks less than a girl wearing high heels.
Why does this happen?
Flat shoes exert less pressure due to more area, while heels exert more pressure on a smaller area. - Case Study 6:
In a science lab, a balloon bursts when overfilled with air.
What causes the balloon to burst?
Air pressure inside exceeds the elastic limit of the balloon’s material. - Case Study 7:
After rubbing a comb on his hair, Anil noticed paper bits jumping toward it.
Which force is responsible here?
Electrostatic force between the charged comb and paper bits. - Case Study 8:
A diver feels more pressure on his body as he dives deeper underwater.
Why does this happen?
Water pressure increases with depth due to the weight of water above. - Case Study 9:
Renu found it easier to push her suitcase when wheels were added.
What made it easier?
Wheels reduce friction, especially rolling friction which is less than sliding friction. - Case Study 10:
Raj drops a tennis ball and a cricket ball simultaneously. Both reach the ground together.
What does this show about gravity?
Gravitational acceleration is the same for all objects in the absence of air resistance. - Case Study 11:
A balloon rubbed against wool sticks to a wall.
Which two forces are acting here?
Electrostatic force between balloon and wall, and gravity pulling balloon downward. - Case Study 12:
During winter, Sneha rubs her palms to feel warm.
Which force helps produce heat here?
Friction between palms converts motion into heat energy. - Case Study 13:
A moving car eventually stops if not accelerated.
What is responsible for bringing it to rest?
Frictional force between tyres and road opposes motion. - Case Study 14:
During a football match, a player kicks the ball and it changes direction.
What does this demonstrate?
Force can change the direction of a moving object. - Case Study 15:
Vikram ties a stone to a rope and swings it in a circle.
What kind of force keeps the stone moving in a circle?
Centripetal force provided by the tension in the rope. - Case Study 16:
A man uses a hydraulic jack to lift a car.
Which principle allows the jack to lift such a heavy load?
Pascal’s Law – pressure applied on a fluid is transmitted equally in all directions. - Case Study 17:
A balloon shrinks in a refrigerator.
What causes this?
Lower temperature reduces internal air pressure, causing the balloon to shrink. - Case Study 18:
Suma finds it difficult to walk on a polished marble floor after it rains.
Why does she experience this?
Wet marble has low friction, causing slipping. - Case Study 19:
Sohan throws a ball upward; it slows down and falls back.
Which forces are acting during the entire motion?
Upward muscular force at start, gravitational force throughout, and air resistance. - Case Study 20:
Priya notices that a dropper sucks in liquid when its bulb is released after pressing.
Why does this happen?
Releasing the bulb creates low pressure inside, and atmospheric pressure pushes the liquid in.
Numericals
- A force of 20 N is applied on an area of 4 m². Calculate the pressure.
Solution:
Pressure = Force / Area = 20 N / 4 m² = 5 Pa
Answer: 5 Pascal
- A man applies a force of 50 N on a surface of area 2.5 m². What is the pressure?
Solution:
Pressure = 50 / 2.5 = 20 Pa
Answer: 20 Pascal
- A force of 200 N is applied on an area of 0.5 m². What is the pressure?
Solution:
Pressure = 200 / 0.5 = 400 Pa
Answer: 400 Pascal
- Calculate the force when pressure is 30 Pa and area is 3 m².
Solution:
Force = Pressure × Area = 30 × 3 = 90 N
Answer: 90 Newton
- What pressure is exerted when a force of 10 N acts on an area of 0.2 m²?
Solution:
Pressure = 10 / 0.2 = 50 Pa
Answer: 50 Pascal
- A person exerts a force of 120 N on a floor with a foot area of 0.015 m². Calculate pressure.
Solution:
Pressure = 120 / 0.015 = 8000 Pa
Answer: 8000 Pascal
- A weight of 600 N is placed on an area of 3 m². What is the pressure?
Solution:
Pressure = 600 / 3 = 200 Pa
Answer: 200 Pascal
- A box weighing 180 N rests on an area of 0.09 m². Calculate pressure.
Solution:
Pressure = 180 / 0.09 = 2000 Pa
Answer: 2000 Pascal
- A force of 250 N is applied on a surface of area 5 m². What is the pressure?
Solution:
Pressure = 250 / 5 = 50 Pa
Answer: 50 Pascal
- Calculate the force needed to exert 1000 Pa of pressure on a 2 m² area.
Solution:
Force = Pressure × Area = 1000 × 2 = 2000 N
Answer: 2000 Newton
- A car tyre touches the ground over an area of 0.02 m². If it supports a weight of 500 N, what pressure does it exert?
Solution:
Pressure = 500 / 0.02 = 25,000 Pa
Answer: 25,000 Pascal
- A pressure of 300 Pa acts over an area of 4 m². What is the force applied?
Solution:
Force = 300 × 4 = 1200 N
Answer: 1200 Newton
- A boy applies a force of 80 N on a door with a contact area of 0.4 m². Find pressure.
Solution:
Pressure = 80 / 0.4 = 200 Pa
Answer: 200 Pascal
- A pressure of 5000 Pa is applied on an area of 0.25 m². What is the force?
Solution:
Force = 5000 × 0.25 = 1250 N
Answer: 1250 Newton
- A cylinder exerts a force of 2000 N on the floor. If the base area is 0.5 m², calculate the pressure.
Solution:
Pressure = 2000 / 0.5 = 4000 Pa
Answer: 4000 Pascal
- A force of 30 N is applied on an object with an area of 6 m². What is the pressure?
Solution:
Pressure = 30 / 6 = 5 Pa
Answer: 5 Pascal
- A box applies pressure of 250 Pa on the floor. If its base area is 0.5 m², calculate force.
Solution:
Force = 250 × 0.5 = 125 N
Answer: 125 Newton
- If a body exerts 400 Pa pressure on 0.1 m² area, find the force.
Solution:
Force = 400 × 0.1 = 40 N
Answer: 40 Newton
- A force of 45 N acts over 0.9 m². Calculate pressure.
Solution:
Pressure = 45 / 0.9 = 50 Pa
Answer: 50 Pascal
- A container exerts 600 N on the floor. The area of contact is 0.3 m². Find the pressure.
Solution:
Pressure = 600 / 0.3 = 2000 Pa
Answer: 2000 Pascal
- A wooden block weighs 100 N and rests on the ground with a base of 2 m². Find the pressure it exerts.
Solution: Pressure = Force / Area = 100 / 2 = 50 Pa
Answer: 50 Pascal
- A metal rod exerts a pressure of 5000 Pa on the floor. If the area is 0.05 m², calculate the force.
Solution: Force = Pressure × Area = 5000 × 0.05 = 250 N
Answer: 250 Newton
- A needle and a coin are both pressed with equal force. Why does the needle pierce but not the coin?
Solution: Needle has a smaller area → higher pressure
Answer: Needle exerts more pressure due to small area
- A water column creates a pressure of 9800 Pa at the base. If the density is 1000 kg/m³ and g = 9.8 m/s², what is the height of the column?
Solution: P = hρg → h = P / (ρg) = 9800 / (1000 × 9.8) = 1 m
Answer: 1 metre
- A book weighing 20 N has dimensions 0.2 m × 0.1 m. If placed flat, what pressure does it exert?
Solution: Area = 0.2 × 0.1 = 0.02 m²; Pressure = 20 / 0.02 = 1000 Pa
Answer: 1000 Pascal
- The same book (from Q25) is placed upright on the 0.1 × 0.05 m face. What pressure is exerted now?
Solution: Area = 0.1 × 0.05 = 0.005 m²; Pressure = 20 / 0.005 = 4000 Pa
Answer: 4000 Pascal
- A balloon bursts at 1200 Pa pressure. If the applied force is 6 N, find the maximum surface area.
Solution: Area = Force / Pressure = 6 / 1200 = 0.005 m²
Answer: 0.005 m²
- A hydraulic lift has a small piston area 0.02 m² and large piston 0.5 m². If 100 N force is applied on the small piston, how much force does the larger piston exert?
Solution: F₁/A₁ = F₂/A₂ → 100/0.02 = F₂/0.5 → F₂ = (100 × 0.5) / 0.02 = 2500 N
Answer: 2500 Newton
- A girl weighing 400 N stands on skis (area = 0.8 m²). Find the pressure on snow.
Solution: Pressure = 400 / 0.8 = 500 Pa
Answer: 500 Pascal
- A man weighing 800 N stands on one foot (area = 0.03 m²). What pressure is exerted?
Solution: Pressure = 800 / 0.03 = 26,667 Pa
Answer: 26,667 Pascal
- A container has a base area of 1 m². If filled with 1000 kg of water, what is the pressure at the base? (Take g = 10 m/s²)
Solution: Weight = 1000 × 10 = 10,000 N; Pressure = 10,000 / 1 = 10,000 Pa
Answer: 10,000 Pascal
- What force must be applied to generate a pressure of 2000 Pa over 0.25 m²?
Solution: Force = Pressure × Area = 2000 × 0.25 = 500 N
Answer: 500 Newton
- A block is pressed against a wall with 120 N force. Contact area is 0.6 m². Calculate the pressure.
Solution: Pressure = 120 / 0.6 = 200 Pa
Answer: 200 Pascal
- A boy exerts 60 N force on a door. If the door contact area is 1.5 m², what pressure is applied?
Solution: Pressure = 60 / 1.5 = 40 Pa
Answer: 40 Pascal
- If the same 60 N force is applied over only 0.3 m², what is the pressure now?
Solution: Pressure = 60 / 0.3 = 200 Pa
Answer: 200 Pascal
- A hammer hits a nail with 150 N force. Tip area is 0.0001 m². Find the pressure.
Solution: Pressure = 150 / 0.0001 = 1,500,000 Pa
Answer: 1,500,000 Pascal
- A pressure of 2500 Pa is exerted by a rectangular object with area 2 m². Find force.
Solution: Force = 2500 × 2 = 5000 N
Answer: 5000 Newton
- A balloon has pressure 2000 Pa inside. External pressure is 1000 Pa. What is the net pressure?
Solution: Net pressure = 2000 – 1000 = 1000 Pa
Answer: 1000 Pascal
- A tyre supports 4000 N over 4 contact patches, each of area 0.02 m². Find pressure per patch.
Solution: Each supports 1000 N; Pressure = 1000 / 0.02 = 50,000 Pa
Answer: 50,000 Pascal
- A 1500 kg car is parked. What is the weight force acting on ground? (g = 9.8 m/s²)
Solution: Force = 1500 × 9.8 = 14,700 N
Answer: 14,700 Newton
- A steel ball exerts a pressure of 10000 Pa on the floor. Contact area is 0.001 m². Find force.
Solution: Force = 10000 × 0.001 = 10 N
Answer: 10 Newton
- A cube of 5 kg mass has 0.25 m² contact area. Find pressure on the surface. (g = 10 m/s²)
Solution: Force = 5 × 10 = 50 N; Pressure = 50 / 0.25 = 200 Pa
Answer: 200 Pascal
- A straw works because of atmospheric pressure. If inner pressure is zero, and area is 0.005 m², what is force from atmospheric pressure? (Take atm pressure = 100,000 Pa)
Solution: Force = 100000 × 0.005 = 500 N
Answer: 500 Newton
- A syringe piston has area 0.01 m² and force applied is 2 N. Calculate pressure inside.
Solution: Pressure = 2 / 0.01 = 200 Pa
Answer: 200 Pascal
- A boy uses a flat wooden plank (area = 0.5 m²) to distribute a weight of 150 N on wet soil. Find pressure.
Solution: Pressure = 150 / 0.5 = 300 Pa
Answer: 300 Pascal
- A liquid in a tube exerts 7500 Pa pressure. Tube cross-sectional area = 0.25 m². Find the force.
Solution: Force = 7500 × 0.25 = 1875 N
Answer: 1875 Newton
- A schoolbag applies 600 N on a child’s shoulders. Strap area = 0.03 m². Calculate pressure.
Solution: Pressure = 600 / 0.03 = 20,000 Pa
Answer: 20,000 Pascal
- A climber with mass 70 kg stands on a ledge with boot area 0.015 m². Calculate pressure. (g = 10 m/s²)
Solution: Force = 70 × 10 = 700 N; Pressure = 700 / 0.015 = 46,667 Pa
Answer: 46,667 Pascal
- A water tank has base area 5 m². It holds 10000 N of water. Find base pressure.
Solution: Pressure = 10000 / 5 = 2000 Pa
Answer: 2000 Pascal
- A man pushes a box with 300 N force over 0.75 m². Calculate pressure.
Solution: Pressure = 300 / 0.75 = 400 Pa
Answer: 400 Pascal
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