Questions & Answers
ICSE - Grade - 9
Subject: Physics
Chapter - 03 - Laws of Motion
Types of Questions
MCQ
- A force is defined as:
a) Anything that produces mass
b) Anything that produces acceleration or deformation
c) Anything that produces energy
d) Anything that changes weight
Answer: b) Anything that produces acceleration or deformation - Which of the following is not an effect of force?
a) Change in direction of motion
b) Production of deformation
c) Increase in mass
d) Acceleration of a body
Answer: c) Increase in mass - The push on a trolley producing motion is an example of:
a) Non-contact force
b) Contact force
c) Magnetic force
d) Balanced force
Answer: b) Contact force - Forces are broadly classified into:
a) Balanced and unbalanced
b) Magnetic and electrostatic
c) Contact and non-contact
d) Static and kinetic
Answer: c) Contact and non-contact - Frictional force always acts:
a) Along the normal to the surface
b) Opposite to relative motion
c) In the direction of motion
d) Vertically upward
Answer: b) Opposite to relative motion - The force exerted by a table on a book kept on it is called:
a) Tension
b) Weight
c) Normal reaction
d) Friction
Answer: c) Normal reaction - Tension in a string is an example of:
a) Contact force
b) Non-contact force
c) Gravitational force
d) Electrostatic force
Answer: a) Contact force - A hammer striking a nail is an example of:
a) Electrostatic force
b) Impact force
c) Tension force
d) Gravitational force
Answer: b) Impact force - Gravitational force is an example of:
a) Non-contact force
b) Contact force
c) Electrostatic force
d) Frictional force
Answer: a) Non-contact force - Electrostatic force is experienced between:
a) Magnets
b) Masses
c) Charged bodies
d) Tension strings
Answer: c) Charged bodies - Newton’s First Law of Motion is also called the law of:
a) Gravitation
b) Inertia
c) Friction
d) Impulse
Answer: b) Inertia - The property of a body to resist change in its state is called:
a) Mass
b) Force
c) Inertia
d) Momentum
Answer: c) Inertia - A passenger lurches forward when a bus stops suddenly due to:
a) Inertia of direction
b) Inertia of motion
c) Inertia of rest
d) Force of friction
Answer: b) Inertia of motion - A heavy table is difficult to move because of:
a) Low inertia
b) High inertia
c) Small force
d) Air resistance
Answer: b) High inertia - The inertia of direction is illustrated when:
a) A book remains on a table until pushed
b) A stone moves tangentially when a string breaks
c) Passengers fall backward when bus starts suddenly
d) Brakes stop a moving car
Answer: b) A stone moves tangentially when a string breaks - Mass is a measure of:
a) Weight
b) Momentum
c) Inertia
d) Energy
Answer: c) Inertia - The SI unit of linear momentum is:
a) kg·m/s
b) N
c) J
d) m/s²
Answer: a) kg·m/s - The linear momentum of a truck of mass 2000 kg moving at 10 m/s is:
a) 200 kg·m/s
b) 20,000 kg·m/s
c) 2000 kg·m/s
d) 2,00,000 kg·m/s
Answer: b) 20,000 kg·m/s - According to Newton’s Second Law, force is equal to:
a) Mass × displacement
b) Mass × acceleration
c) Mass × velocity
d) Mass ÷ acceleration
Answer: b) Mass × acceleration - Which law gives the definition of force?
a) First law
b) Second law
c) Third law
d) Law of gravitation
Answer: b) Second law - SI unit of force is:
a) Dyne
b) Newton
c) Joule
d) Watt
Answer: b) Newton - 1 Newton is equal to:
a) 1 g·cm/s²
b) 1 kg·m/s²
c) 1 kg·cm/s
d) 10⁵ dynes
Answer: b) 1 kg·m/s² - 1 dyne is equal to:
a) 1 kg·m/s²
b) 10⁻⁵ N
c) 10⁵ N
d) 1 N
Answer: b) 10⁻⁵ N - Newton’s Third Law states:
a) Every object resists change in motion
b) Force equals mass × acceleration
c) To every action there is an equal and opposite reaction
d) Gravitational force acts between two bodies
Answer: c) To every action there is an equal and opposite reaction - The recoil of a gun is an example of:
a) Newton’s First Law
b) Newton’s Second Law
c) Newton’s Third Law
d) Law of Gravitation
Answer: c) Newton’s Third Law - The universal law of gravitation states that:
a) All bodies repel each other
b) Every two masses attract with a force proportional to their product and inversely proportional to the square of distance
c) The Earth attracts bodies with equal force
d) Mass and weight are equal
Answer: b) Every two masses attract with a force proportional to their product and inversely proportional to the square of distance - The formula for gravitational force is:
a) F = m a
b) F = G m₁ m₂ / r²
c) F = m v
d) F = k q₁ q₂ / r²
Answer: b) F = G m₁ m₂ / r² - Acceleration due to gravity on Earth is approximately:
a) 8.9 m/s²
b) 9.8 m/s²
c) 10.8 m/s²
d) 6.7 m/s²
Answer: b) 9.8 m/s² - Expression for g in terms of G, M, and R is:
a) g = GM/R
b) g = GM/R²
c) g = GR/M²
d) g = M/G R²
Answer: b) g = GM/R² - Weight of a body is given by:
a) W = m g
b) W = m v
c) W = F/m
d) W = GM/R²
Answer: a) W = m g - Free fall means:
a) Falling under air resistance
b) Falling under force of tension
c) Falling under gravity alone
d) Falling under magnetic force
Answer: c) Falling under gravity alone - Which quantity is constant everywhere?
a) Weight
b) Mass
c) Acceleration due to gravity
d) Force
Answer: b) Mass - Weight varies with:
a) Force applied
b) Mass of body
c) Value of g
d) Momentum
Answer: c) Value of g - Unit of mass is:
a) Newton
b) Joule
c) Kilogram
d) Dyne
Answer: c) Kilogram - A ball of 0.2 kg moving at 10 m/s is brought to rest in 0.05 s. The average force is:
a) 20 N
b) 30 N
c) 40 N
d) 50 N
Answer: c) 40 N - Impulse is equal to:
a) Rate of change of momentum
b) Force × displacement
c) Change in momentum
d) Mass × acceleration
Answer: c) Change in momentum - When a man walks, the ground pushes him forward. This is explained by:
a) First law
b) Second law
c) Third law
d) Gravitation
Answer: c) Third law - When a book rests on a table, the table exerts a force equal to:
a) Zero
b) Mass of book
c) Weight of book
d) Twice the weight of book
Answer: c) Weight of book - The gravitational force between two 1 kg masses kept 1 m apart is:
a) 6.67×10⁻¹¹ N
b) 9.8 N
c) 1 N
d) Zero
Answer: a) 6.67×10⁻¹¹ N - The SI unit of impulse is:
a) N/s
b) N·m
c) N·s
d) J
Answer: c) N·s - Which law gives the definition of inertia?
a) First Law
b) Second Law
c) Third Law
d) Gravitation
Answer: a) First Law - Inertia increases with:
a) Force
b) Acceleration
c) Mass
d) Velocity
Answer: c) Mass - The type of friction that prevents a body from starting motion is:
a) Kinetic friction
b) Static friction
c) Rolling friction
d) Sliding friction
Answer: b) Static friction - The highest value of static friction is called:
a) Kinetic friction
b) Limiting friction
c) Normal reaction
d) Impact force
Answer: b) Limiting friction - When palms are rubbed against each other, the force in action is:
a) Normal reaction
b) Tension
c) Kinetic friction
d) Electrostatic force
Answer: c) Kinetic friction - The SI unit of acceleration due to gravity is:
a) m/s
b) m/s²
c) N/kg
d) J
Answer: b) m/s² - Force required to stop a moving body depends on:
a) Mass only
b) Velocity only
c) Change of momentum
d) Time only
Answer: c) Change of momentum - Inertia of rest is demonstrated when:
a) Passenger falls back when bus starts suddenly
b) Passenger falls forward when bus stops suddenly
c) Stone moves tangentially on breaking of string
d) Gun recoils backward
Answer: a) Passenger falls back when bus starts suddenly - Work done by gravitational force on a falling body is:
a) Positive
b) Negative
c) Zero
d) Constant
Answer: a) Positive - Mass of a body is constant but weight depends on:
a) Place on Earth
b) Speed of body
c) Volume of body
d) Shape of body
Answer: a) Place on Earth
Fill in the Blanks
- A ______ is any influence that tends to change the state of rest or uniform motion of a body.
Answer: force - Force can produce acceleration or ______ in a body.
Answer: retardation - A force can produce ______ or deformation in a body.
Answer: rotation - The force exerted by a table on a book placed on it is called ______.
Answer: normal reaction - Frictional force always acts ______ to the surfaces in contact.
Answer: tangential - Frictional force always acts ______ to the direction of motion or impending motion.
Answer: opposite - The force exerted during a hammer striking a nail is called ______ force.
Answer: impact (collision) - Attraction between Earth and Moon is an example of ______ force.
Answer: gravitational - Electrostatic force exists between two ______ objects.
Answer: charged - Magnetic force exists between ______ poles.
Answer: like or unlike - Newton’s First Law of Motion is also known as the law of ______.
Answer: inertia - A body continues in its state of rest or uniform motion unless acted upon by an external ______.
Answer: force - The property of a body to resist change in its state is called ______.
Answer: inertia - Mass is a measure of ______.
Answer: inertia - A heavy truck is harder to stop than a bicycle because of greater ______.
Answer: inertia - Inertia of rest is shown when a passenger falls ______ when the bus starts suddenly.
Answer: backward - Inertia of motion is shown when a passenger falls ______ when the bus stops suddenly.
Answer: forward - A stone tied to a string moves tangentially when the string breaks due to inertia of ______.
Answer: direction - The SI unit of mass is ______.
Answer: kilogram (kg) - The SI unit of force is ______.
Answer: newton (N) - One newton is equal to ______.
Answer: 1 kg·m/s² - The CGS unit of force is ______.
Answer: dyne - One dyne is equal to ______ newton.
Answer: 10⁻⁵ - The momentum of a body is given by the formula p = ______.
Answer: m v - The SI unit of momentum is ______.
Answer: kg·m/s - Change in momentum is given by ______.
Answer: m(vf − vi) - Rate of change of momentum is equal to ______.
Answer: force - Newton’s Second Law defines ______.
Answer: force - According to Newton’s Second Law, F = ______.
Answer: ma - Impulse is equal to change in ______.
Answer: momentum - The SI unit of impulse is ______.
Answer: newton-second (N·s) - To every action there is an equal and opposite ______.
Answer: reaction - The recoil of a gun is explained by Newton’s ______ Law of Motion.
Answer: Third - Walking is possible because the ground exerts a forward ______.
Answer: reaction force - Gravitational force between two masses is given by F = ______.
Answer: G m₁ m₂ / r² - The value of acceleration due to gravity on Earth is approximately ______ m/s².
Answer: 9.8 - Weight of a body is given by W = ______.
Answer: m g - Relation between g and G is g = ______.
Answer: GM / R² - Motion of a body under gravity alone is called ______.
Answer: free fall - In free fall, all bodies fall with the same ______.
Answer: acceleration due to gravity (g) - Mass of a body is constant, but weight varies with ______.
Answer: g (acceleration due to gravity) - Mass is a ______ quantity, while weight is a vector quantity.
Answer: scalar - The unit of weight is ______.
Answer: newton (N) - The gravitational constant G has a value of ______.
Answer: 6.67 × 10⁻¹¹ N·m²/kg² - Force due to collision acts for a very ______ time.
Answer: short - Friction is caused by microscopic ______ of surfaces.
Answer: irregularities - Braking of a vehicle is possible due to ______ between brake pad and wheel.
Answer: friction - The Earth attracts the Moon due to ______ force.
Answer: gravitational - A book resting on a table illustrates the balance between weight and ______.
Answer: normal reaction - Mass of a body does not change with ______.
Answer: place or position
Name the Following
- The influence that tends to change the state of rest or uniform motion of a body.
Answer: Force - The force exerted by surfaces perpendicular to the area of contact.
Answer: Normal reaction force - The force that opposes relative motion between two surfaces in contact.
Answer: Frictional force - The pulling force transmitted through a string.
Answer: Tension force - The force exerted during a hammer striking a nail.
Answer: Impact (collision) force - The attractive force acting between any two masses.
Answer: Gravitational force - The force of attraction or repulsion between charged bodies.
Answer: Electrostatic force - The force of attraction or repulsion between magnetic poles.
Answer: Magnetic force - The law that states every object continues in its state of rest or uniform motion unless acted upon by an external force.
Answer: Newton’s First Law of Motion - The property of a body by virtue of which it resists change in its state.
Answer: Inertia - The kind of inertia shown when a passenger falls backward as a bus starts suddenly.
Answer: Inertia of rest - The kind of inertia shown when a passenger falls forward when a bus stops suddenly.
Answer: Inertia of motion - The kind of inertia shown when a stone tied to a string moves tangentially on breaking of the string.
Answer: Inertia of direction - The measure of inertia of a body.
Answer: Mass - The product of mass and velocity of a body.
Answer: Linear momentum - The law which defines force.
Answer: Newton’s Second Law of Motion - The law which states “To every action there is an equal and opposite reaction.”
Answer: Newton’s Third Law of Motion - The SI unit of force.
Answer: Newton - The CGS unit of force.
Answer: Dyne - The relation between Newton and dyne.
Answer: 1 dyne = 10⁻⁵ N - The effect of a force acting for a very short time during collision.
Answer: Impulse - The SI unit of impulse.
Answer: Newton-second (N·s) - The expression F = ma is derived from which law of motion?
Answer: Newton’s Second Law of Motion - The universal constant of gravitation.
Answer: G (gravitational constant) - The value of acceleration due to gravity on Earth.
Answer: 9.8 m/s² - The formula for acceleration due to gravity in terms of G, M, and R.
Answer: g = GM/R² - The force experienced by a body due to Earth’s gravity.
Answer: Weight - The motion of a body under gravity alone.
Answer: Free fall - The quantity which remains constant everywhere in the universe.
Answer: Mass - The quantity which varies from place to place due to change in g.
Answer: Weight - The SI unit of mass.
Answer: Kilogram (kg) - The vector quantity among mass and weight.
Answer: Weight - The scalar quantity among mass and weight.
Answer: Mass - The law that explains why a gun recoils backwards when fired.
Answer: Newton’s Third Law of Motion - The law that explains why a moving truck is harder to stop than a bicycle.
Answer: Newton’s First Law of Motion - The force that acts even without direct contact.
Answer: Non-contact force - The force that arises only due to physical contact.
Answer: Contact force - The SI unit of momentum.
Answer: kg·m/s - The mathematical expression for momentum.
Answer: p = mv - The relation between force and rate of change of momentum.
Answer: F = dp/dt - The universal law which explains the attraction between Earth and Moon.
Answer: Universal Law of Gravitation - The short-duration large force acting during a collision.
Answer: Impact force - The property of bodies that fall with the same acceleration irrespective of mass.
Answer: Free fall - The force which resists motion between brake pad and wheel in a moving vehicle.
Answer: Frictional force - The scientist who formulated the three laws of motion.
Answer: Sir Isaac Newton - The law that gives the definition of momentum.
Answer: Newton’s Second Law of Motion - The quantity defined as force per unit mass experienced by a body due to gravity.
Answer: Acceleration due to gravity (g) - The constant G in gravitation has a value of ______.
Answer: 6.67 × 10⁻¹¹ N·m²/kg² - The force responsible for the attraction of iron filings towards a magnet.
Answer: Magnetic force - The type of friction that prevents the start of motion.
Answer: Static friction
Answer in One Word
- The flow of electric charge is called?
Answer: Current - The SI unit of electric current?
Answer: Ampere - Electric current is measured by?
Answer: Ammeter - The instrument used to measure potential difference?
Answer: Voltmeter - The SI unit of potential difference?
Answer: Volt - The potential difference between the ends of a conductor causes?
Answer: Current - The charge of an electron is?
Answer: Negative - The conventional direction of current is from?
Answer: Positive - The unit of electric charge?
Answer: Coulomb - A device which converts chemical energy into electrical energy?
Answer: Cell - A group of cells arranged together is called?
Answer: Battery - A cell that cannot be recharged is called?
Answer: Primary - A cell that can be recharged is called?
Answer: Secondary - A Daniell cell is a type of?
Answer: Primary - A lead-acid cell is a type of?
Answer: Secondary - The electrode in a dry cell is made of?
Answer: Zinc - The electrolyte in a dry cell is?
Answer: Ammonium chloride - The electrode in a lead-acid battery is made of?
Answer: Lead - The electrolyte in a lead-acid cell is?
Answer: Sulphuric acid - The current produced by cells is?
Answer: Direct - The SI unit of resistance?
Answer: Ohm - The instrument used to regulate current?
Answer: Rheostat - The relation between current, potential difference, and resistance is given by?
Answer: Ohm’s Law - The graph between current and potential difference for a metallic conductor is a?
Answer: Straight line - The resistance of a conductor depends on its length, material, and?
Answer: Area - The device used to protect circuits from overloading?
Answer: Fuse - The heating effect of current is used in?
Answer: Iron - The SI unit of electrical power?
Answer: Watt - The commercial unit of electrical energy?
Answer: Kilowatt-hour - The instrument used to measure energy consumed?
Answer: Meter - The power consumed in a circuit is given by?
Answer: P=VI - The filament of an electric bulb is made of?
Answer: Tungsten - The property of a conductor that opposes current?
Answer: Resistance - A resistor obeying Ohm’s law is called?
Answer: Ohmic - The substance which offers negligible resistance to current?
Answer: Superconductor - The work done in moving one coulomb charge through a potential difference of 1 volt?
Answer: Joule - The law stating current is directly proportional to potential difference is?
Answer: Ohm’s - The international standard unit of electric energy?
Answer: Joule - The device used for producing large currents in laboratories?
Answer: Battery - The electrolyte in a Daniell cell is?
Answer: Copper sulphate - In a dry cell, the depolarizer used is?
Answer: Manganese dioxide - A secondary cell commonly used in vehicles?
Answer: Lead-acid - The resistance of a wire increases with its?
Answer: Length - The resistance of a wire decreases with increase in its?
Answer: Area - The resistance of a metallic conductor increases with?
Answer: Temperature - The rate of flow of charge is?
Answer: Current - The electric current in household supply is?
Answer: Alternating - The SI unit of resistivity?
Answer: Ohm-metre - The effect of current used in an electric heater?
Answer: Heating - The chemical effect of current is used in?
Answer: Electroplating
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
- Force, Mass, Acceleration, Temperature
Answer: Temperature – It is not related to Newton’s laws of motion. - Friction, Tension, Normal reaction, Pressure
Answer: Pressure – It is not a contact force but a physical quantity. - Gravitational force, Magnetic force, Electrostatic force, Friction
Answer: Friction – It is a contact force, others are non-contact. - Inertia of rest, Inertia of motion, Inertia of direction, Acceleration
Answer: Acceleration – It is not a type of inertia. - Book on a table, Man walking, Gun recoil, Car engine working
Answer: Car engine working – It is not an example of Newton’s third law. - Momentum, Impulse, Mass, Resistance
Answer: Resistance – It belongs to electricity, not mechanics. - Dyne, Newton, Joule, Kilogram-force
Answer: Joule – It is unit of work, not force. - Mass, Weight, Force, Acceleration due to gravity
Answer: Mass – It is constant, others vary with gravity. - Truck braking, Stone tied to string, Book on table, Bulb glowing
Answer: Bulb glowing – Not an example of mechanics/forces. - Action, Reaction, Inertia, Impulse
Answer: Inertia – It is a property, others involve forces. - Push, Pull, Velocity, Collision
Answer: Velocity – It is not a force. - Newton’s first law, Newton’s second law, Newton’s third law, Law of floatation
Answer: Law of floatation – It belongs to Archimedes’ principle, not Newton’s laws. - Acceleration, Retardation, Inertia, Momentum
Answer: Inertia – It is a property, not a motion parameter. - Gun recoil, Walking, Swimming, Reading
Answer: Reading – Not related to Newton’s third law. - kg, m, s, Ampere
Answer: Ampere – It is a unit of current, not mechanics. - Free fall, Projectile, Weight, Friction
Answer: Friction – Not related to motion under gravity. - G (universal constant), g (acceleration due to gravity), Mass, Resistance
Answer: Resistance – Belongs to electricity, not gravitation. - Spring force, Normal reaction, Tension, Capacitance
Answer: Capacitance – Not a force. - Book on a table, Walking, Swimming, Ball at rest
Answer: Ball at rest – It shows inertia, not action-reaction. - Truck, Bicycle, Train, Bulb
Answer: Bulb – Not related to momentum or motion. - Newton, Dyne, Joule, Kilogram-force
Answer: Joule – It is work, others are force. - Stone tied to string, Gun recoil, Foot on ground, Sound wave
Answer: Sound wave – Not an example of Newton’s third law. - Acceleration, Force, Work, Momentum
Answer: Work – It is energy, others are mechanics quantities. - Push, Pull, Inertia, Friction
Answer: Inertia – Property of matter, not force. - Dyne, Newton, Watt, Kilogram-force
Answer: Watt – Unit of power, not force. - Normal reaction, Friction, Weight, Mass
Answer: Mass – It is not a force. - Momentum, Inertia, Tension, Collision
Answer: Tension – A force, others are motion properties. - Gravitational force, Electrostatic force, Friction, Torque
Answer: Torque – It is turning effect, not force of interaction. - Walking, Swimming, Running, Sleeping
Answer: Sleeping – No motion involved. - Ball hitting bat, Hammer hitting nail, Book at rest, Vehicle crash
Answer: Book at rest – Not a case of collision. - Newton’s First Law, Newton’s Second Law, Newton’s Third Law, Archimedes’ Principle
Answer: Archimedes’ Principle – Belongs to fluids. - Weight, Force, Acceleration, Mass
Answer: Mass – Not a vector. - Book on a table, Car engine, Gun recoil, Walking
Answer: Car engine – Not an action-reaction example. - F = ma, p = m v, W = mg, I = V/R
Answer: I = V/R – Belongs to electricity. - Free fall, Projectile, Elastic collision, Evaporation
Answer: Evaporation – Belongs to heat. - Push, Pull, Tension, Work
Answer: Work – Not a force. - Heavy table, Truck in motion, Glass at rest, String tension
Answer: String tension – A force, others illustrate inertia. - g = GM/R², F = ma, p = m v, V = IR
Answer: V = IR – Belongs to electricity. - Collision, Explosion, Recoil, Photosynthesis
Answer: Photosynthesis – Belongs to biology. - Walking, Swimming, Flying, Sleeping
Answer: Sleeping – No force interaction. - Joule, Newton, Dyne, Kilogram-force
Answer: Joule – Unit of work. - Momentum, Velocity, Acceleration, Mass
Answer: Mass – Scalar, others are vectors. - Gravitational force, Magnetic force, Electrostatic force, Normal reaction
Answer: Normal reaction – It is contact, others non-contact. - Inertia of rest, Inertia of motion, Inertia of direction, Momentum
Answer: Momentum – Not a type of inertia. - Car crash, Hammer on nail, Book at rest, Ball hitting bat
Answer: Book at rest – Not collision. - Acceleration, Retardation, Force, Temperature
Answer: Temperature – Not mechanics. - Free fall, Projectile, Orbital motion, Friction
Answer: Friction – Contact force, others due to gravity. - Joule, Watt, Newton, Dyne
Answer: Watt – Power, others force. - Walking, Gun recoil, Swimming, Reading
Answer: Reading – No action-reaction. - Mass, Inertia, Weight, Resistance
Answer: Resistance – Electrical property, others mechanical.
Match the Pair
Set 1
Column A
- Force
- Friction
- Normal reaction
- Tension in string
- Impact force
Column B
a. Large force during collision
b. Opposes relative motion
c. Pull transmitted through a string
d. Acts perpendicular to surface
e. Causes acceleration or deformation
Answers:
1 – e
2 – b
3 – d
4 – c
5 – a
Set 2
Column A
- Newton’s First Law
- Newton’s Second Law
- Newton’s Third Law
- Inertia of motion
- Inertia of rest
Column B
a. Every action has equal and opposite reaction
b. A moving body resists change in motion
c. Law of inertia
d. F = ma
e. Body at rest resists motion
Answers:
1 – c
2 – d
3 – a
4 – b
5 – e
Set 3
Column A
- Mass
- Weight
- Linear momentum
- Impulse
- Rate of change of momentum
Column B
a. Vector quantity = mv
b. Scalar measure of matter
c. F × Δt
d. Force due to gravity = mg
e. dp/dt
Answers:
1 – b
2 – d
3 – a
4 – c
5 – e
Set 4
Column A
- Static friction
- Kinetic friction
- Book on table
- Rubbing palms
- Braking vehicle
Column B
a. Friction that opposes motion in progress
b. Resists motion at rest
c. Friction prevents slipping
d. Produces heat while moving
e. Stops motion using friction
Answers:
1 – b
2 – a
3 – c
4 – d
5 – e
Set 5
Column A
- Free fall
- Gravitational force
- g on Earth
- Universal law of gravitation
- Relationship between g and G
Column B
a. Acceleration of body under gravity alone
b. F = G m₁ m₂ / r²
c. g = GM / R²
d. Attraction between masses
e. ≈ 9.8 m/s²
Answers:
1 – a
2 – d
3 – e
4 – b
5 – c
Set 6
Column A
- Inertia of direction
- Stone tied to string released
- Heavy truck harder to stop
- Moving bus stops suddenly
- Passengers lurch forward
Column B
a. Inertia resists change of direction
b. Example of inertia of motion
c. Example of inertia due to mass
d. Demonstrates inertia of motion
e. Stone moves tangentially
Answers:
1 – a
2 – e
3 – c
4 – d
5 – b
Set 7
Column A
- Compressed spring
- Mass suspended from ceiling
- Two masses over pulley
- Hammer striking nail
- Ball hitting bat
Column B
a. Example of tension in string
b. Example of impact force
c. Force transmitted along light string
d. Force due to deformation
e. Force during collision
Answers:
1 – d
2 – a
3 – c
4 – e
5 – b
Set 8
Column A
- Electrostatic force
- Magnetic force
- Walking
- Gun recoil
- Earth–Moon attraction
Column B
a. Action-reaction between foot and ground
b. Attraction between masses
c. Attraction/repulsion between poles
d. Attraction/repulsion between charges
e. Recoil due to action-reaction
Answers:
1 – d
2 – c
3 – a
4 – e
5 – b
Set 9
Column A
- F = ma
- dp/dt
- Impulse-momentum theorem
- Book sliding on plane
- Car skids on road
Column B
a. F = rate of change of momentum
b. Slows due to kinetic friction
c. Δp = F Δt
d. Force proportional to acceleration
e. Resists motion due to insufficient grip
Answers:
1 – d
2 – a
3 – c
4 – b
5 – e
Set 10
Column A
- Mass
- Weight
- g on Moon
- Mass vs weight
- Heavy object on table
Column B
a. Resists acceleration (inertia)
b. Force due to gravity
c. Smaller than on Earth
d. Mass constant, weight varies with g
e. Example of inertia of rest
Answers:
1 – a
2 – b
3 – c
4 – d
5 – e
Short Answer Questions
- What is the definition of force?
Answer: A force is any influence that tends to change the state of rest or uniform motion of a body, or produces deformation. - Name the types of forces.
Answer: Contact forces and non-contact forces. - Give an example of a contact force.
Answer: Friction between a book and table. - Give an example of a non-contact force.
Answer: Gravitational attraction between Earth and Moon. - What is friction?
Answer: Friction is the force that opposes relative motion between two surfaces in contact. - What is normal reaction?
Answer: Normal reaction is the force exerted by a surface on a body, perpendicular to the surface. - What is tension in a string?
Answer: Tension is the pulling force transmitted along a light, inextensible string. - What is impact force?
Answer: Impact force is a large contact force exerted during a collision. - Give an example of static friction.
Answer: A book resting on an inclined plane. - Give an example of kinetic friction.
Answer: Rubbing palms together. - What is Newton’s first law of motion?
Answer: Every object continues in its state of rest or uniform motion unless acted upon by an external force. - Define inertia.
Answer: Inertia is the property of a body to resist any change in its state of rest or motion. - What is the inertia of rest?
Answer: The tendency of a body at rest to remain at rest until acted upon by a force. - What is inertia of motion?
Answer: The tendency of a moving body to continue in motion unless acted upon by a force. - What is inertia of direction?
Answer: The tendency of a body to continue moving in the same direction unless acted upon by a force. - How is mass related to inertia?
Answer: Mass is a measure of inertia; greater mass means greater inertia. - What is linear momentum?
Answer: Linear momentum is the product of mass and velocity of a body, p = mv. - State the formula for change of momentum.
Answer: Δp = m(v_f − v_i) - What is the rate of change of momentum?
Answer: It is the force acting on a body, given by dp/dt. - State Newton’s second law of motion.
Answer: The rate of change of momentum of a body is proportional to the applied force and in the direction of the force. - Give the formula for F = ma.
Answer: F = m × a, where m is mass and a is acceleration. - Give the SI unit of force.
Answer: Newton (N) - Give the CGS unit of force.
Answer: Dyne - State Newton’s third law of motion.
Answer: To every action, there is an equal and opposite reaction. - Give an example of action-reaction pair.
Answer: Foot pushes ground while walking; ground pushes foot. - State the universal law of gravitation.
Answer: Every particle of matter attracts every other particle with a force proportional to the product of their masses and inversely proportional to the square of the distance between them. - Give the formula for weight of a body.
Answer: W = m × g - Give the formula for acceleration due to gravity.
Answer: g = GM / R² - Define free fall.
Answer: Free fall is the motion of a body under the influence of gravity alone, neglecting air resistance. - How do mass and weight differ?
Answer: Mass is constant and scalar; weight is a force, vector, and varies with g. - Give an example of gravitational force.
Answer: Attraction between Earth and Moon. - Give an example of electrostatic force.
Answer: A charged comb attracting paper bits. - Give an example of magnetic force.
Answer: Bar magnet attracting iron filings. - What is the effect of force on a body?
Answer: Force can produce acceleration, change direction, cause rotation, or deformation. - What is the effect of friction on motion?
Answer: Friction opposes motion and can produce heat. - How does a compressed spring exert force?
Answer: It exerts a restoring force when released. - What is the impulse experienced by a body?
Answer: Impulse is the product of force and the time during which it acts. - How is impulse related to momentum?
Answer: Impulse equals the change in momentum of a body. - What happens to a moving stone if the string breaks?
Answer: It continues in a tangential path due to inertia of direction. - What is observed when a moving bus stops suddenly?
Answer: Passengers lurch forward due to inertia of motion. - How is F = ma derived from dp/dt?
Answer: For constant mass, dp/dt = m × dv/dt = m × a → F = ma. - What is the role of normal reaction on an inclined plane?
Answer: It balances the component of weight perpendicular to the plane. - Give an example of tension in a string.
Answer: Two masses connected over a pulley. - Give an example of impact force.
Answer: A ball hitting a bat. - Why is a truck harder to stop than a bicycle?
Answer: Because it has greater mass and hence greater inertia. - Why is friction useful in walking?
Answer: It provides grip between shoes and ground. - Why do all bodies fall with the same acceleration in vacuum?
Answer: Because free fall acceleration depends only on gravity, not mass. - Give an example of static friction in daily life.
Answer: A book resting on a table. - Give an example of kinetic friction in daily life.
Answer: Braking a vehicle. - Why does a gun recoil when fired?
Answer: Due to action-reaction forces; the bullet moves forward and the gun moves backward.
Puzzles
- Q: I am the property of a body that resists change in motion. What am I?
A: Inertia - Q: I act at a distance without contact. I keep the Moon in orbit. Who am I?
A: Gravitational force - Q: I am the product of mass and velocity. What am I?
A: Linear momentum - Q: I oppose motion between surfaces in contact. Who am I?
A: Friction - Q: I am measured in Newtons. I change motion of objects. Who am I?
A: Force - Q: I act perpendicular to a surface supporting a body. Who am I?
A: Normal reaction - Q: I transmit pulling force through a string. What am I?
A: Tension - Q: When I hit a ball, I change its momentum over time. What am I?
A: Impulse - Q: I keep a moving object moving in the same direction unless a force acts. Who am I?
A: Inertia of direction - Q: I resist starting motion of a stationary object. Who am I?
A: Static friction - Q: I oppose motion of a moving object. Who am I?
A: Kinetic friction - Q: I am a force that always acts along the line joining two masses. Who am I?
A: Gravitational force - Q: I am the force that arises from interaction of charges. Who am I?
A: Electrostatic force - Q: I attract magnetic materials and repel/attract poles. Who am I?
A: Magnetic force - Q: I state that every object continues in its state of rest or uniform motion unless acted upon. What am I?
A: Newton’s First Law - Q: I quantify how fast momentum changes. Who am I?
A: Force (dp/dt) - Q: I am a formula derived from Newton’s Second Law: F = ?
A: F = ma - Q: I occur when a hammer strikes a nail. What am I?
A: Impact force - Q: I cause a ball to stop when a bat hits it. Who am I?
A: Impulse - Q: I always acts opposite to impending motion. Who am I?
A: Limiting friction - Q: I keep your feet from slipping when walking. Who am I?
A: Friction - Q: I balance the weight of a book on a table. Who am I?
A: Normal reaction - Q: I act along the string connecting two masses over a pulley. Who am I?
A: Tension - Q: I result from F = dp/dt. What am I?
A: Force - Q: I keep planets revolving around the Sun. Who am I?
A: Gravitational force - Q: I vary with location but mass remains constant. What am I?
A: Weight - Q: I cause passengers to lurch forward in a bus. Who am I?
A: Inertia of motion - Q: I oppose relative motion but generate heat. Who am I?
A: Friction - Q: I am always perpendicular to the surface supporting a body. Who am I?
A: Normal reaction - Q: I explain why heavier trucks are harder to stop. Who am I?
A: Greater inertia due to mass - Q: I act over distance, attracting all masses. Who am I?
A: Gravity - Q: I am equal and opposite to the force you exert. Who am I?
A: Reaction force (Newton’s Third Law) - Q: I keep a body at rest until force is applied. Who am I?
A: Inertia of rest - Q: I oppose motion in vehicles during braking. Who am I?
A: Kinetic friction - Q: I am used to calculate weight: W = ?
A: W = mg - Q: I am the acceleration experienced by a body in free fall. Who am I?
A: g - Q: I act on a body to change its velocity. Who am I?
A: Force - Q: I am the rate of change of momentum. Who am I?
A: Force - Q: I cause equal and opposite reactions in rockets. Who am I?
A: Newton’s Third Law - Q: I am always directed along the line joining centers of mass. Who am I?
A: Gravitational force - Q: I reduce sliding between tires and road. Who am I?
A: Friction - Q: I am maximum for a body at rest. Who am I?
A: Limiting friction - Q: I am smaller once the object starts moving. Who am I?
A: Kinetic friction - Q: I make it difficult to start motion for a heavy object. Who am I?
A: Inertia of rest - Q: I explain why a gun recoils when fired. Who am I?
A: Newton’s Third Law - Q: I store energy when deformed and exert force when released. Who am I?
A: Compressed spring - Q: I depend only on gravitational field, not mass. Who am I?
A: Acceleration due to gravity (g) - Q: I cause braking distance to be longer for trucks. Who am I?
A: Greater momentum - Q: I am measured in kg·m/s. Who am I?
A: Momentum - Q: I explain why objects continue moving if no external force acts. Who am I?
A: Newton’s First Law (Law of Inertia)
Difference Between:
- Q: Difference between Mass and Weight
A:
- Mass is the amount of matter in a body; scalar quantity; SI unit: kg; remains constant everywhere.
- Weight is the force due to gravity acting on a body; vector quantity; SI unit: N; varies with location (depends on g).
- Q: Difference between Inertia of Rest and Inertia of Motion
A:
- Inertia of Rest: Tendency of a body to remain at rest until an external force acts. Example: Glass on a table stays at rest until pushed.
- Inertia of Motion: Tendency of a moving body to continue moving at same speed in same direction unless acted upon. Example: Passengers lurch forward when a bus stops suddenly.
- Q: Difference between Contact Forces and Non-Contact Forces
A:
- Contact Forces: Require physical contact to act. Example: Friction, tension.
- Non-Contact Forces: Act at a distance without physical contact. Example: Gravitational, electrostatic, magnetic forces.
- Q: Difference between Static Friction and Kinetic Friction
A:
- Static Friction: Acts on stationary objects; prevents start of motion; varies up to a maximum (limiting friction).
- Kinetic Friction: Acts on moving objects; opposes motion; usually smaller than limiting friction.
- Q: Difference between Force and Pressure
A:
- Force: Push or pull on an object causing acceleration or deformation; vector quantity; SI unit: N.
- Pressure: Force applied per unit area; scalar quantity; SI unit: Pa (N/m²).
- Q: Difference between Impulse and Force
A:
- Impulse: Product of force and time; changes momentum; vector quantity.
- Force: Rate of change of momentum; acts at an instant; vector quantity.
- Q: Difference between Mass and Inertia
A:
- Mass: Amount of matter in a body; scalar; measured in kg.
- Inertia: Property of body resisting change in state of motion; increases with mass; no unit.
- Q: Difference between Linear Momentum and Impulse
A:
- Linear Momentum (p): Product of mass and velocity (p = mv); vector quantity; SI unit: kg·m/s.
- Impulse: Product of force and time interval; equal to change in momentum; vector; SI unit: N·s.
- Q: Difference between Weight and Gravitational Force
A:
- Weight: Force experienced by a body due to gravity at a specific location (W = mg).
- Gravitational Force: Universal attractive force between any two masses (F = G m₁ m₂ / r²).
- Q: Difference between Normal Reaction and Tension
A:
- Normal Reaction: Perpendicular force exerted by surface on body in contact. Example: Book on table.
- Tension: Pulling force transmitted through a string, rope, or cable. Example: Mass suspended from ceiling.
- Q: Difference between Newton’s First Law and Newton’s Second Law
A:
- First Law: Law of inertia; body continues in uniform motion or at rest unless acted upon by external force.
- Second Law: Quantitative law; rate of change of momentum is proportional to applied force (F = dp/dt or F = ma).
- Q: Difference between Newton’s Second Law and Newton’s Third Law
A:
- Second Law: Describes how force affects motion of a single body.
- Third Law: Describes interaction between two bodies; every action has equal and opposite reaction.
- Q: Difference between Inertia of Direction and Inertia of Motion
A:
- Inertia of Direction: Tendency of a moving body to continue in the same direction. Example: Stone on string moves tangentially when string breaks.
- Inertia of Motion: Tendency to continue moving at same speed in same direction; includes magnitude of velocity.
- Q: Difference between Impact Force and Frictional Force
A:
- Impact Force: Large, short-duration force during collision; changes momentum. Example: Ball hitting bat.
- Frictional Force: Acts tangentially, opposite to motion or impending motion; long-duration effect. Example: Braking of vehicle.
- Q: Difference between Universal Gravitation and Gravitational Acceleration
A:
- Universal Gravitation: F = G m₁ m₂ / r²; acts between any two masses.
- Gravitational Acceleration (g): Acceleration experienced by a body due to Earth’s gravity; g = GM/R² ≈ 9.8 m/s².
- Q: Difference between Velocity and Acceleration
A:
- Velocity: Rate of change of displacement; vector; m/s.
- Acceleration: Rate of change of velocity; vector; m/s².
- Q: Difference between Kinetic Energy and Work Done by Force
A:
- Kinetic Energy: Energy possessed due to motion; KE = ½ mv².
- Work Done: Product of force and displacement in the direction of force; W = F·d.
- Q: Difference between Limiting Friction and Kinetic Friction
A:
- Limiting Friction: Maximum static friction before motion starts; prevents motion.
- Kinetic Friction: Friction acting on moving body; smaller than limiting friction; opposes motion.
- Q: Difference between Action Force and Reaction Force
A:
- Action Force: Force applied by first body on second.
- Reaction Force: Force applied by second body on first; equal in magnitude, opposite in direction.
- Q: Difference between Free Fall and Motion under Gravity
A:
- Free Fall: Motion of body under gravity alone, ignoring air resistance; all objects accelerate equally.
- Motion under Gravity: Includes resistances like air; acceleration may vary.
Assertion and Reason
1.
A: A heavy truck is harder to stop than a bicycle.
R: Inertia of a body increases with its mass.
Answer: Both A and R are true, and R is the correct explanation of A.
A: A book on a table remains at rest.
R: The net force acting on the book is zero.
Answer: Both A and R are true, and R is the correct explanation of A.
A: A moving ball continues in motion unless acted upon by a force.
R: This is an example of Newton’s first law of motion.
Answer: Both A and R are true, and R is the correct explanation of A.
A: A car accelerates when a greater force is applied.
R: Newton’s second law states that force is proportional to the rate of change of momentum.
Answer: Both A and R are true, and R is the correct explanation of A.
A: The tension in a string transmits force.
R: A string pulls equally on both connected bodies.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Friction always opposes motion.
R: Microscopic irregularities of surfaces cause friction.
Answer: Both A and R are true, and R is the correct explanation of A.
A: A hammer striking a nail exerts a large force over a short time.
R: This force is called an impact force.
Answer: Both A and R are true, and R is the correct explanation of A.
A: A moving bus suddenly stops and passengers lurch forward.
R: This demonstrates inertia of motion.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Mass is the measure of inertia.
R: Heavier bodies resist motion change more than lighter bodies.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Force is measured in Newtons.
R: 1 N = 1 kg·m/s².
Answer: Both A and R are true, and R is the correct explanation of A.
A: Electrostatic forces act at a distance.
R: Like charges repel and unlike charges attract.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Magnetic forces can attract or repel.
R: Similar poles repel, opposite poles attract.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Weight of a body on Earth is W = mg.
R: Weight is the force due to gravity acting on mass.
Answer: Both A and R are true, and R is the correct explanation of A.
A: All bodies fall with the same acceleration under gravity in vacuum.
R: Free fall neglects air resistance.
Answer: Both A and R are true, and R is the correct explanation of A.
A: F = ma is derived from F = dp/dt.
R: For constant mass, dp/dt = m dv/dt.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Newton’s third law applies to walking.
R: The foot pushes the ground and the ground pushes the foot equally in opposite direction.
Answer: Both A and R are true, and R is the correct explanation of A.
A: A compressed spring exerts force on an obstacle.
R: Deformation produces a restoring force.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Impulse changes the momentum of a body.
R: Impulse = Force × Time of application.
Answer: Both A and R are true, and R is the correct explanation of A.
A: A book on an inclined plane remains at rest.
R: Static friction prevents motion until a threshold force is exceeded.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Normal reaction acts perpendicular to the surface.
R: It balances the component of weight perpendicular to the plane.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Momentum p = mv is a vector quantity.
R: Its direction is the same as that of velocity.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Mass remains constant on Earth and Moon.
R: Mass is a scalar quantity and independent of gravity.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Weight varies with location.
R: Weight depends on gravitational acceleration g.
Answer: Both A and R are true, and R is the correct explanation of A.
A: A block sliding on a rough surface slows down.
R: Kinetic friction opposes motion.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Newton’s first law is also called the law of inertia.
R: It states that a body resists change in motion unless acted upon by a force.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Acceleration is directly proportional to force.
R: F = ma implies force and acceleration are proportional.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Mass of a body resists acceleration.
R: Greater mass requires greater force to achieve the same acceleration.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Impact force is usually very large.
R: It acts over a very short time interval.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Tension in a string is the same throughout a light, inextensible string.
R: The string transmits force equally to both ends.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Acceleration of free fall on Earth is 9.8 m/s².
R: g = GM/R², where M is Earth’s mass and R its radius.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Friction is useful in walking.
R: Friction provides grip between shoes and ground.
Answer: Both A and R are true, and R is the correct explanation of A.
A: A moving stone continues tangentially if string breaks.
R: This demonstrates inertia of direction.
Answer: Both A and R are true, and R is the correct explanation of A.
A: A rocket moving in space experiences action-reaction forces.
R: Exhaust gases push backward and rocket moves forward.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Impulse experienced by a body is equal to change in momentum.
R: Impulse-momentum theorem states Δp = F Δt.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Mass measures the quantity of matter in a body.
R: Mass is independent of shape and size of body.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Weight is the force due to gravity.
R: Weight is a vector and depends on g at location.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Kinetic friction is usually less than static friction.
R: Static friction resists initiation of motion, kinetic friction resists motion in progress.
Answer: Both A and R are true, and R is the correct explanation of A.
A: A car skids on a road during sudden braking.
R: Tires lose grip due to insufficient friction.
Answer: Both A and R are true, and R is the correct explanation of A.
A: Heavier objects are harder to push than lighter ones.
R: More mass increases inertia.
Answer: Both A and R are true, and R is the correct explanation of A.
A: F = dp/dt is Newton’s second law in general form.
R: For constant mass, it reduces to F = ma.
Answer: Both A and R are true, and R is the correct explanation of A.
True or False
- Force is any influence that can change the state of motion of a body.
Answer: True - Friction always assists the motion of a body.
Answer: False - Normal reaction acts perpendicular to the surface in contact.
Answer: True - Tension in a string is a type of non-contact force.
Answer: False - Impact force acts over a large duration of time.
Answer: False - Gravitational force acts at a distance between two masses.
Answer: True - Electrostatic force exists only when objects are in contact.
Answer: False - Magnetic force can attract or repel depending on the poles.
Answer: True - Newton’s first law of motion is also called the law of inertia.
Answer: True - Inertia is a property of a body to resist change in its state of rest or motion.
Answer: True - Mass is a measure of inertia and varies with location.
Answer: False - Weight is a scalar quantity.
Answer: False - Momentum is given by p = mv and is a vector quantity.
Answer: True - Impulse = Force × Time and changes the momentum of a body.
Answer: True - Newton’s second law states that force is inversely proportional to acceleration.
Answer: False - F = dp/dt is the general form of Newton’s second law.
Answer: True - For constant mass, F = dp/dt reduces to F = ma.
Answer: True - Newton’s third law states that action and reaction forces act on the same body.
Answer: False - A truck is easier to stop than a bicycle of lesser mass.
Answer: False - Static friction prevents motion until a threshold force is applied.
Answer: True - Kinetic friction opposes motion of a body already in motion.
Answer: True - The weight of a body is the same on Earth and Moon.
Answer: False - g = GM/R² gives the acceleration due to gravity on a planet.
Answer: True - In free fall, all bodies fall with the same acceleration neglecting air resistance.
Answer: True - A book on a table experiences only normal reaction.
Answer: False - Tension in a light, inextensible string is uniform throughout.
Answer: True - Friction is never useful in daily life.
Answer: False - A compressed spring exerts force when released.
Answer: True - Mass and weight are always numerically equal.
Answer: False - Linear momentum is conserved in absence of external force.
Answer: True - Impulse has the same direction as the force applied.
Answer: True - Inertia of direction makes a moving stone continue tangentially when string breaks.
Answer: True - Walking demonstrates action-reaction pairs according to Newton’s third law.
Answer: True - A moving bus stopping suddenly is an example of inertia of motion.
Answer: True - Heavier objects are harder to accelerate due to greater inertia.
Answer: True - Newton’s second law is applicable only when mass varies with time.
Answer: False - Friction produces rotation in some cases.
Answer: True - Impact force is generally small and of long duration.
Answer: False - A ball falling freely under gravity experiences a force equal to its weight.
Answer: True - The rate of change of momentum is equal to the net force acting on a body.
Answer: True - Action and reaction forces cancel each other out when acting on different bodies.
Answer: False - Electrostatic forces are always attractive.
Answer: False - Magnetic forces can act without contact.
Answer: True - Acceleration produced in a body is independent of the applied force.
Answer: False - A heavy table is harder to move than a light chair due to larger inertia.
Answer: True - Weight is independent of the gravitational acceleration of the planet.
Answer: False - F = ma can be derived from the general form F = dp/dt.
Answer: True - The normal reaction on an inclined plane is always vertical.
Answer: False - A stone tied to a string moving in a circle continues in a circular path when released.
Answer: False - Momentum and impulse have the same units in SI system.
Answer: False
Long Answer Questions
- Q: Define force and explain its effects.
A: A force is any influence that tends to change the state of rest or uniform motion of a body, or produces deformation. Effects include: producing acceleration or retardation, changing the direction of motion, producing rotation or deformation, and neutralizing another force (equilibrium). - Q: Distinguish between contact and non-contact forces with examples.
A: Contact forces arise due to physical contact between bodies, e.g., friction, tension, normal reaction. Non-contact forces act at a distance without physical contact, e.g., gravitational force, magnetic force, electrostatic force. - Q: What is friction? List its types with examples.
A: Friction is the force that opposes relative motion between surfaces in contact. Types:
- Static friction: prevents motion of a stationary object (book on an inclined plane).
- Limiting friction: maximum static friction before motion starts.
- Kinetic friction: opposes motion of a moving object (rubbing palms, braking a vehicle).
- Q: Explain normal reaction force with examples.
A: Normal reaction is the perpendicular force exerted by a surface on a body in contact. Examples: book on a table (R = mg), block on an inclined plane (R perpendicular to plane). - Q: Define tension force and give examples.
A: Tension is the pulling force transmitted along a light, inextensible string. Examples: mass suspended from a ceiling, two masses connected over a pulley. - Q: What is impact force and impulse? Give examples.
A: Impact force is a large contact force during a collision. Impulse is the product of force and time of application, equal to change in momentum. Examples: ball hitting a bat, vehicle crash, hammer striking a nail. - Q: Define gravitational force with examples.
A: Gravitational force is the attractive force between any two masses. Examples: weight of a body on Earth, Earth–Moon attraction. - Q: Explain electrostatic and magnetic forces with examples.
A: Electrostatic force acts between charged objects (like repel, unlike attract); e.g., charged comb attracting paper bits. Magnetic force acts between magnets or magnetic materials (like poles repel, unlike poles attract); e.g., bar magnet attracting iron filings. - Q: State Newton’s First Law of Motion and give examples.
A: Every object continues in its state of rest or uniform motion in a straight line unless acted upon by an external force. Examples: a ball on a smooth floor remains stationary; a moving hockey puck continues moving unless stopped by friction. - Q: Define inertia. What are its kinds? Give examples.
A: Inertia is the property of a body to resist change in its state of rest or motion. Kinds:
- Inertia of rest: body at rest resists motion (glass on table).
- Inertia of motion: moving body resists stopping (passengers lurch forward in bus).
- Inertia of direction: body resists change in direction (stone moves tangentially when string breaks).
- Q: How is mass related to inertia?
A: Mass is a measure of inertia. The larger the mass of a body, the greater its resistance to change in motion or rest. Example: a heavy truck is harder to start or stop than a bicycle. - Q: Define linear momentum and give its SI unit.
A: Linear momentum is the product of mass and velocity of a body, p = mv. SI unit: kg·m/s. Example: a 2000 kg truck moving at 10 m/s has momentum 20,000 kg·m/s. - Q: Explain change and rate of change of momentum.
A: Change of momentum: Δp = m(v_f − v_i).
Rate of change of momentum: dp/dt = Force. This shows that force acting on a body changes its momentum. - Q: State Newton’s Second Law of Motion.
A: The rate of change of momentum of a body is proportional to the applied force and in the direction of the force. For constant mass, F = ma. - Q: Derive F = ma from F = dp/dt.
A: Momentum, p = mv.
Rate of change of momentum: dp/dt = m dv/dt = ma.
Hence, F = ma. - Q: Give the SI and CGS units of force.
A: SI unit: Newton (N), where 1 N = 1 kg·m/s².
CGS unit: Dyne, where 1 dyne = 10⁻⁵ N. - Q: State Newton’s Third Law of Motion with examples.
A: To every action there is an equal and opposite reaction. Examples:
- Book on table: weight acts downward, normal reaction acts upward.
- Walking: foot pushes ground, ground pushes foot.
- Gun recoil: bullet moves forward, gun moves backward.
- Q: Explain universal law of gravitation.
A: Every particle of matter attracts every other particle with a force proportional to the product of their masses and inversely proportional to the square of the distance between them: F = G m₁ m₂ / r². - Q: Define weight and give its formula.
A: Weight is the force due to gravity acting on a body. Formula: W = mg, where g is acceleration due to gravity. - Q: Derive relation between g and G.
A: From universal law: F = GMm / R². Weight: W = mg = GMm / R² → g = GM / R². - Q: Define free fall and state its properties.
A: Free fall is motion under gravity alone, neglecting air resistance. All bodies fall with same acceleration g irrespective of mass. - Q: Differentiate mass and weight.
A: Mass: amount of matter, scalar, constant, unit kg.
Weight: force due to gravity, vector, varies with g, unit N. - Q: Give examples of contact and non-contact forces.
A: Contact: friction, tension, normal reaction. Non-contact: gravitational, electrostatic, magnetic forces. - Q: Explain static, limiting, and kinetic friction with examples.
A:
- Static: prevents motion (book on table).
- Limiting: maximum before motion starts.
- Kinetic: opposes motion in progress (braking vehicle, rubbing palms).
- Q: How does a moving bus demonstrate inertia?
A: Passengers lurch forward when bus stops suddenly due to inertia of motion. - Q: How does a stone demonstrate inertia of direction?
A: When string breaks, stone moves tangentially, showing it continues in same direction. - Q: Give examples of tension in strings.
A: Mass suspended from ceiling, two masses over a pulley. - Q: Give examples of impact force.
A: Ball hitting bat, hammer striking nail, vehicle crash. - Q: How is impulse related to momentum?
A: Impulse = Force × Time = Change in momentum (Δp). - Q: Explain why heavier objects are harder to move.
A: Greater mass means greater inertia, so more force is needed to accelerate or decelerate. - Q: Explain walking using Newton’s third law.
A: Foot pushes ground backward (action), ground pushes foot forward (reaction), propelling the person. - Q: Explain gun recoil using Newton’s third law.
A: Bullet moves forward (action), gun moves backward (reaction) due to equal and opposite forces. - Q: Explain effect of force on a body.
A: Force can cause acceleration, retardation, change in direction, rotation, or deformation depending on nature and point of application. - Q: How does a compressed spring exert force?
A: When released, the deformation produces a restoring force along the spring. - Q: What is the role of kinetic friction in braking?
A: Kinetic friction between brake pads and wheels slows and stops the vehicle. - Q: Explain why friction is useful in daily life.
A: Friction allows walking, gripping objects, driving vehicles, and stopping motion safely. - Q: Explain uniform motion using Newton’s first law.
A: A body continues in straight line at constant speed unless an external force acts, e.g., hockey puck sliding on ice. - Q: Explain why mass remains constant everywhere.
A: Mass is a measure of matter and is independent of location or gravitational field. - Q: Why does weight vary with location?
A: Weight depends on gravitational acceleration g, which varies with planetary body or altitude. - Q: How does a moving vehicle demonstrate inertia of motion?
A: Vehicle resists stopping immediately due to inertia; passengers lurch forward when brakes are applied.
Give Reasons
- Q: Why does a stationary book on a table not move?
A: Because of inertia of rest; it resists change in its state of rest. - Q: Why does a moving bus stop cause passengers to lurch forward?
A: Due to inertia of motion; the passengers continue moving when the bus stops. - Q: Why does a stone move tangentially when the string breaks?
A: Due to inertia of direction; it continues in the same direction it was moving. - Q: Why is it harder to move a heavy truck than a bicycle?
A: Greater mass means greater inertia, requiring more force to accelerate. - Q: Why does friction oppose motion?
A: Because microscopic irregularities of surfaces resist relative movement. - Q: Why is static friction usually greater than kinetic friction?
A: Because it resists the initiation of motion, needing more force to overcome. - Q: Why does a book on an inclined plane remain at rest?
A: Static friction balances the component of weight along the plane. - Q: Why does a compressed spring exert force when released?
A: Because deformation stores potential energy which produces a restoring force. - Q: Why does a ball rebound when it hits a wall?
A: Because of impact force; the change in momentum causes the rebound. - Q: Why does a moving car skid on a slippery road?
A: Because kinetic friction is reduced, so the tires cannot grip the surface effectively. - Q: Why does a heavy table require more force to move?
A: Because greater mass means greater inertia of rest. - Q: Why does a ball dropped in vacuum fall with the same acceleration as a heavier one?
A: Because acceleration due to gravity is independent of mass. - Q: Why is mass constant everywhere but weight varies?
A: Mass is the amount of matter, while weight depends on gravitational acceleration. - Q: Why does a gun recoil when a bullet is fired?
A: Due to Newton’s third law; the forward action on bullet produces equal and opposite reaction on the gun. - Q: Why does walking require friction?
A: Friction provides grip between feet and ground, preventing slipping. - Q: Why is a puck on ice able to move long distances with minimal force?
A: Because friction is very low, so it opposes motion minimally. - Q: Why does F = ma apply only when mass is constant?
A: Because Newton’s second law in general form is F = dp/dt; for constant mass, dp/dt = m × a. - Q: Why do heavier objects resist acceleration more?
A: Due to greater inertia proportional to their mass. - Q: Why does a suspended mass over a pulley remain in equilibrium until released?
A: Because the tension in the string balances the weight of the mass. - Q: Why does a book exert weight on a table?
A: Because gravity pulls it downward with a force equal to mg. - Q: Why does normal reaction act perpendicular to the surface?
A: Because it balances the component of weight perpendicular to the surface. - Q: Why does a ball experience impulse when struck?
A: Because force applied over a short time changes its momentum. - Q: Why does a moving hockey puck continue straight unless acted upon?
A: Due to Newton’s first law; it continues in uniform motion unless a force acts. - Q: Why does friction produce heat?
A: Because work done against friction converts mechanical energy into thermal energy. - Q: Why does a truck require more braking distance than a car?
A: Because larger mass means larger momentum, requiring more force or distance to stop. - Q: Why does a stone on a string continue along tangential path when string snaps?
A: Because no force acts toward the center; inertia of direction makes it move tangentially. - Q: Why is kinetic friction always less than limiting friction?
A: Because once motion starts, surfaces slide over each other more easily. - Q: Why do objects in free fall accelerate at the same rate?
A: Because acceleration depends only on gravitational field, not on mass. - Q: Why does impulse equal change in momentum?
A: From Newton’s second law, F × Δt = Δp. - Q: Why is action and reaction observed simultaneously?
A: Because forces in Newton’s third law are equal in magnitude and opposite in direction. - Q: Why does a hockey puck slide further on ice than on carpet?
A: Because friction on ice is lower, offering less resistance to motion. - Q: Why does mass measure inertia?
A: Greater mass resists acceleration more, showing resistance to motion change. - Q: Why does a book on a table not accelerate vertically?
A: Because normal reaction balances its weight. - Q: Why does a moving passenger continue forward when bus stops?
A: Due to inertia; body resists sudden change in motion. - Q: Why does the moon not fall into Earth?
A: Because it has tangential velocity and gravity provides centripetal force for orbit. - Q: Why is tension uniform in a light string?
A: Because the string is massless, so force is transmitted equally. - Q: Why does braking generate heat?
A: Friction converts kinetic energy into thermal energy. - Q: Why does F = GMm/r² apply universally?
A: Because gravitational attraction exists between all masses, proportional to product of masses and inverse square of distance. - Q: Why does mass not depend on location?
A: Mass is the amount of matter, independent of gravitational field. - Q: Why does weight vary from Earth to Moon?
A: Because weight depends on local g, which is smaller on the Moon. - Q: Why does a moving ball on smooth floor continue unless stopped?
A: Due to inertia; no net external force is acting. - Q: Why is friction necessary for vehicles to move safely?
A: Friction allows tires to grip the road and prevents slipping. - Q: Why does a stone resist motion when at rest?
A: Due to inertia of rest. - Q: Why does a hammer drive a nail when struck?
A: Impact force transfers momentum to nail, driving it into the surface. - Q: Why do action-reaction forces not cancel?
A: Because they act on different bodies. - Q: Why does F = ma reduce from F = dp/dt for constant mass?
A: Because dp/dt = m × dv/dt = ma when mass is constant. - Q: Why is static friction useful?
A: It prevents slipping of objects at rest. - Q: Why does kinetic friction oppose motion?
A: Because surfaces in relative motion resist sliding. - Q: Why is normal reaction zero in free fall?
A: Because there is no surface in contact to exert the force. - Q: Why do two bodies of different masses fall at same rate in vacuum?
A: Because acceleration depends only on gravity, not on mass.
Arrange the Words
Case Studies
Case Study 1
A bus suddenly stops at a traffic signal. Passengers inside lurch forward.
Q: Explain why this happens.
A: Due to inertia of motion; the passengers tend to continue in motion while the bus stops.
Case Study 2
A heavy block is placed on a smooth table and a small force is applied. The block hardly moves.
Q: Why is it difficult to move the block?
A: Because of its large mass (inertia of rest) and friction opposing motion.
Case Study 3
A ball falls from a height and hits the ground, bouncing back.
Q: Explain why the ball bounces.
A: Impact force changes momentum during collision, producing a rebound.
Case Study 4
A stone tied to a string is whirled in a circle. The string suddenly breaks.
Q: What happens to the stone? Why?
A: It moves tangentially to the circle due to inertia of direction.
Case Study 5
A truck and a bicycle move at the same speed. Brakes are applied simultaneously.
Q: Which stops first and why?
A: Bicycle stops first; truck has more mass, greater momentum, requiring more distance to stop.
Case Study 6
A person pushes a trolley across a rough floor.
Q: Why does the trolley move slowly?
A: Friction opposes motion, and part of applied force is used to overcome it.
Case Study 7
A rocket launches upward, pushing exhaust gases downwards.
Q: Explain the motion of the rocket.
A: By Newton’s Third Law, action of gases downward produces equal and opposite reaction, propelling rocket upward.
Case Study 8
A hockey puck slides on ice and stops after a long distance.
Q: Why does it eventually stop?
A: Small kinetic friction acts over distance, gradually reducing its momentum.
Case Study 9
A book rests on a table.
Q: Identify all forces acting on the book.
A: Weight downward due to gravity and normal reaction upward; forces are equal and opposite.
Case Study 10
A ball is suspended by a string and is pulled aside. On release, it swings back.
Q: Why does the string exert force on the ball?
A: Tension in the string transmits force, changing direction of motion.
Case Study 11
A car brakes suddenly, causing luggage to slide forward.
Q: Why does the luggage move?
A: Due to inertia of motion; luggage tends to continue moving forward when car stops.
Case Study 12
A book on an inclined plane does not slide.
Q: Which friction is responsible and why?
A: Static friction; it opposes motion until the component of weight along the plane exceeds it.
Case Study 13
Two 1 kg masses are placed 1 m apart.
Q: Calculate gravitational force between them using G = 6.67 × 10⁻¹¹ N·m²/kg².
A: F = GM₁M₂ / r² = (6.67 × 10⁻¹¹ × 1 × 1) / 1² = 6.67 × 10⁻¹¹ N
Case Study 14
A truck moving at 10 m/s has mass 2000 kg.
Q: Calculate its linear momentum.
A: p = mv = 2000 × 10 = 20,000 kg·m/s
Case Study 15
A spring is compressed by a hammer strike.
Q: Why does the spring push back on the hammer?
A: Deformation stores potential energy; spring exerts restoring force.
Case Study 16
A person tries to move a heavy desk. It does not move until pushed hard.
Q: Which kind of friction is acting initially?
A: Limiting static friction; it resists the initiation of motion.
Case Study 17
A satellite orbits the Earth without falling to the surface.
Q: Why does it not crash?
A: Tangential velocity causes centripetal motion; gravity provides the inward force, keeping it in orbit.
Case Study 18
A ball is thrown upwards; it rises, stops momentarily, and falls down.
Q: Explain the motion using Newton’s laws.
A: Gravity exerts downward force; upward motion slows (retardation) due to F = ma; then it accelerates downward.
Case Study 19
A truck applies brakes on a slippery road and skids.
Q: Why does skidding occur?
A: Friction is reduced on slippery surface; insufficient to stop the truck quickly.
Case Study 20
Two objects with different masses are dropped in vacuum from same height.
Q: Which falls faster and why?
A: Both fall at same rate; acceleration depends only on gravity, not mass.
Numericals
Numerical 1
Q: A force of 20 N acts on a 5 kg body. Find its acceleration.
A: Using F = ma, a = F/m = 20/5 = 4 m/s²
Numerical 2
Q: A 0.2 kg ball moving at 10 m/s is brought to rest in 0.05 s. Find the force exerted on it.
A: F = Δp / Δt = m(v_f − v_i)/t = 0.2(0 − 10)/0.05 = −40 N
Magnitude of force = 40 N
Numerical 3
Q: Two 1 kg masses are 1 m apart. Find gravitational force (G = 6.67 × 10⁻¹¹ N·m²/kg²).
A: F = G m₁ m₂ / r² = (6.67 × 10⁻¹¹ × 1 × 1)/1² = 6.67 × 10⁻¹¹ N
Numerical 4
Q: A 2000 kg truck moves at 10 m/s. Find its linear momentum.
A: p = mv = 2000 × 10 = 20,000 kg·m/s
Numerical 5
Q: A 10 kg body is pushed with a force of 50 N. Find acceleration.
A: F = ma → a = F/m = 50/10 = 5 m/s²
Numerical 6
Q: A 0.5 kg ball is thrown vertically upward at 20 m/s. Find its momentum at release.
A: p = mv = 0.5 × 20 = 10 kg·m/s
Numerical 7
Q: A 5 kg block slides on a rough surface with kinetic friction 10 N. Applied force = 40 N. Find acceleration.
A: Net force = 40 − 10 = 30 N → a = F/m = 30/5 = 6 m/s²
Numerical 8
Q: A 2 kg mass falls from 10 m height. Find force due to gravity.
A: W = mg = 2 × 9.8 = 19.6 N
Numerical 9
Q: A 3 kg ball accelerates at 4 m/s². Find the applied force.
A: F = ma = 3 × 4 = 12 N
Numerical 10
Q: Two 5 kg bodies collide elastically. Velocity of first body changes from 6 m/s to 2 m/s. Find impulse.
A: Δp = m Δv = 5(2 − 6) = −20 kg·m/s
Magnitude = 20 kg·m/s
Numerical 11
Q: A 500 kg car accelerates from rest to 20 m/s in 10 s. Find the force applied.
A: a = Δv/t = 20/10 = 2 m/s² → F = ma = 500 × 2 = 1000 N
Numerical 12
Q: A body of 10 kg experiences a retardation of 2 m/s². Find force applied opposite to motion.
A: F = ma = 10 × 2 = 20 N
Numerical 13
Q: A stone of 0.1 kg is dropped from 5 m height. Find velocity just before hitting ground (g = 10 m/s²).
A: v = √(2gh) = √(2 × 10 × 5) = √100 = 10 m/s
Numerical 14
Q: A 0.2 kg ball moving at 5 m/s is stopped in 0.1 s. Find force exerted.
A: F = mΔv/Δt = 0.2 × (0 − 5)/0.1 = −10 N
Magnitude = 10 N
Numerical 15
Q: A 50 kg boy jumps from a height of 2 m. Find his weight on Earth (g = 9.8 m/s²).
A: W = mg = 50 × 9.8 = 490 N
Numerical 16
Q: A body of mass 10 kg moving at 5 m/s collides and stops in 0.5 s. Find average force.
A: F = mΔv/Δt = 10 × (0 − 5)/0.5 = −100 N
Magnitude = 100 N
Numerical 17
Q: A 1 kg ball is thrown at 15 m/s. Find its momentum.
A: p = mv = 1 × 15 = 15 kg·m/s
Numerical 18
Q: A truck of mass 2000 kg accelerates at 1 m/s². Find force applied.
A: F = ma = 2000 × 1 = 2000 N
Numerical 19
Q: A 5 kg body moves under a 25 N force. Find acceleration.
A: a = F/m = 25/5 = 5 m/s²
Numerical 20
Q: Two 2 kg bodies are 2 m apart. Find gravitational force.
A: F = G m₁ m₂ / r² = 6.67 × 10⁻¹¹ × 2 × 2 / 4 = 6.67 × 10⁻¹¹ N
Numerical 21
Q: A 10 kg body moves with 6 m/s. Find linear momentum.
A: p = mv = 10 × 6 = 60 kg·m/s
Numerical 22
Q: A 0.5 kg ball hits a bat, stopping from 15 m/s in 0.05 s. Find force.
A: F = mΔv/Δt = 0.5 × (0 − 15)/0.05 = −150 N
Magnitude = 150 N
Numerical 23
Q: A 2 kg mass on frictionless table is pulled by 10 N. Find acceleration.
A: a = F/m = 10/2 = 5 m/s²
Numerical 24
Q: A 5 kg block on rough surface experiences friction 5 N; applied force = 15 N. Find acceleration.
A: Net F = 15 − 5 = 10 N → a = F/m = 10/5 = 2 m/s²
Numerical 25
Q: A ball of 0.2 kg moving at 10 m/s is reversed to 5 m/s in 0.1 s. Find force.
A: F = mΔv/Δt = 0.2 × (−15)/0.1 = −30 N
Magnitude = 30 N
Numerical 26
Q: A 3 kg body moving at 6 m/s is stopped in 0.2 s. Find force.
A: F = mΔv/Δt = 3 × (0 − 6)/0.2 = −90 N
Magnitude = 90 N
Numerical 27
Q: A mass of 4 kg experiences acceleration 3 m/s². Find force.
A: F = ma = 4 × 3 = 12 N
Numerical 28
Q: A 0.5 kg ball is dropped from 20 m. Find velocity before impact (g = 10 m/s²).
A: v = √(2gh) = √(2 × 10 × 20) = √400 = 20 m/s
Numerical 29
Q: A car of 1000 kg accelerates at 2 m/s². Find force.
A: F = ma = 1000 × 2 = 2000 N
Numerical 30
Q: Two 1 kg balls are 1 m apart. Find F_grav.
A: F = 6.67 × 10⁻¹¹ × 1 × 1 / 1² = 6.67 × 10⁻¹¹ N
Numerical 31
Q: A 10 kg box accelerated by 50 N. Find acceleration.
A: a = F/m = 50/10 = 5 m/s²
Numerical 32
Q: 5 kg ball moving at 3 m/s is stopped in 0.2 s. Find force.
A: F = mΔv/Δt = 5 × (0 − 3)/0.2 = −75 N
Numerical 33
Q: A 2000 kg truck accelerates from 0 to 10 m/s in 20 s. Find the force applied.
A: a = Δv/Δt = 10/20 = 0.5 m/s² → F = ma = 2000 × 0.5 = 1000 N
Numerical 34
Q: A 0.3 kg ball moving at 8 m/s is brought to rest in 0.1 s. Find the average force.
A: F = mΔv/Δt = 0.3 × (0 − 8)/0.1 = −24 N
Magnitude = 24 N
Numerical 35
Q: A block of 10 kg rests on a horizontal surface. Find normal reaction.
A: R = mg = 10 × 9.8 = 98 N
Numerical 36
Q: A 0.2 kg ball moving at 5 m/s strikes a wall and rebounds at 3 m/s. Find change in momentum.
A: Δp = m(v_f − v_i) = 0.2 × (−3 − 5) = −1.6 kg·m/s
Magnitude = 1.6 kg·m/s
Numerical 37
Q: A 5 kg mass is hanging from a ceiling via a string. Find tension in string.
A: T = mg = 5 × 9.8 = 49 N
Numerical 38
Q: A 0.5 kg ball falls from 10 m. Find time of fall (g = 10 m/s²).
A: h = ½ g t² → t² = 2h/g = 20/10 = 2 → t = √2 ≈ 1.414 s
Numerical 39
Q: A 2 kg body experiences force 20 N along surface with friction 5 N. Find acceleration.
A: Net force = 20 − 5 = 15 N → a = F/m = 15/2 = 7.5 m/s²
Numerical 40
Q: Two 3 kg masses are 2 m apart. Find gravitational force.
A: F = G m₁ m₂ / r² = 6.67 × 10⁻¹¹ × 3 × 3 / 4 = 1.50 × 10⁻¹⁰ N
Numerical 41
Q: A 0.1 kg ball is thrown at 20 m/s. Find its momentum.
A: p = mv = 0.1 × 20 = 2 kg·m/s
Numerical 42
Q: A 50 kg object falls freely from height 5 m. Find velocity just before hitting ground (g = 10 m/s²).
A: v = √(2gh) = √(2 × 10 × 5) = √100 = 10 m/s
Numerical 43
Q: A car of mass 1000 kg accelerates at 3 m/s². Find force.
A: F = ma = 1000 × 3 = 3000 N
Numerical 44
Q: A ball of 0.2 kg moving at 10 m/s hits a wall and rebounds at 6 m/s. Find impulse.
A: Δp = m(v_f − v_i) = 0.2 × (−6 − 10) = −3.2 kg·m/s
Magnitude = 3.2 kg·m/s
Numerical 45
Q: A 5 kg box moves on horizontal surface under 25 N applied force; friction = 5 N. Find acceleration.
A: Net F = 25 − 5 = 20 N → a = F/m = 20/5 = 4 m/s²
Numerical 46
Q: A stone of mass 0.5 kg is whirled in a circle of radius 2 m at 5 m/s. Find centripetal force.
A: F = m v² / r = 0.5 × 25 / 2 = 6.25 N
Numerical 47
Q: A body of 2 kg moving at 10 m/s is stopped in 0.2 s. Find force.
A: F = mΔv/Δt = 2 × (0 − 10)/0.2 = −100 N
Magnitude = 100 N
Numerical 48
Q: A 10 kg box is pulled with 60 N; friction = 10 N. Find acceleration.
A: Net F = 60 − 10 = 50 N → a = F/m = 50/10 = 5 m/s²
Numerical 49
Q: A ball of 0.3 kg moving at 6 m/s stops in 0.1 s. Find average force.
A: F = mΔv/Δt = 0.3 × (0 − 6)/0.1 = −18 N
Magnitude = 18 N
Numerical 50
Q: Two 2 kg bodies 1 m apart. Find gravitational force.
A: F = G m₁ m₂ / r² = 6.67 × 10⁻¹¹ × 2 × 2 / 1² = 2.668 × 10⁻¹⁰ N
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