These Class 9 Science MCQ and Class 9 Science Exploration Chapter 6 MCQ Online Test with Answers How Forces Affect Motion focus on both theory and practical applications.
Class 9 Science Chapter 6 How Forces Affect Motion MCQ
How Forces Affect Motion MCQ
Class 9 Science Chapter 6 MCQ Online Test
Question 1.
Which of the following statements is true about buoyant force and gravitational force?
(a) Both forces act in the same direction
(b) Buoyant force acts upward and gravitational force acts downward
(c) Buoyant force acts downward and gravitational force acts upward
(d) Both forces act only when the object is solid
Answer:
(b) Buoyant force acts upward and gravitational force acts downward
Question 2.
A spring balance is used to measure
(a) volume
(b) density
(c) force or weight
(d) speed
Answer:
(c) force or weight
Question 3.
A batsman hits a cricket ball which then rolls on a level ground. After covering a short distance, the ball comes to rest. The ball slows to a stop because
(a) the batsman did not hit the ball hard enough
(b) velocity is proportional to the force exerted on the ball
(c) there is a force between the ball and ground opposing the motion
(d) there is no unbalanced force on the ball so the ball would tend to come to rest
Answer:
(c) there is a force between the ball and ground opposing the motion
Question 4.
According to the third law of motion, action and reaction (NCERT Exemplar)
(a) always act on the same body
(b) always act on different bodies in opposite directions
(c) have same magnitude and directions
(d) act on either body at normal to each other
Answer:
(b) always act on different bodies in opposite directions
Question 5.
Which of the following statements is not correct for an object moving along a straight path in an accelerated motion?
(a) Its speed keeps changing
(b) Its velocity always changes
(c) It always goes away from the earth
(d) A force is always acting on it
Answer:
(c) It always goes away from the earth
Question 6.
A goalkeeper in a game of football pulls his hands backwards after holding the ball shot at the goal. This enables the goalkeeper to (NCERT Exemplar)
(a) exert larger force on the ball
(b) reduce the force exerted by the ball on hands
(c) increase the rate of change of momentum
(d) decrease the rate of change of momentum.
Answer:
(b) reduce the force exerted by the ball on hands
Question 7.
A water tanker filled up to 2/3 of its height is moving with a uniform speed. On sudden application of the brake, the water in the tank would (NCERT Exemplar)
(a) move forward
(b) move backward
(c) be unaffected
(d) rise upwards
Answer:
(b) move backward
Question 8.
The magnitude of the acceleration is
(a) proportional to the magnitude of the net force and is inversely proportional to the mass of the object
(b) proportional to the mass and is inversely proportional to the magnitude of the net force
(c) proportional to mass only
(d) inversely proportional to the net force only
Answer:
(a) proportional to the magnitude of the net force and is inversely proportional to the mass of the object
Question 9.
When we stop pedaling the bicycle, it stops because
(a) the Earth’s gravitational force acts on it
(b) it is not accelerated
(c) no unbalanced force acts on it
(d) frictional force acts on it
Answer:
(d) frictional force acts on it
Question 10.
When a body is suspended from a spring balance, the elongation produced is directly proportional to
(a) mass of the body
(b) volume of the body
(c) weight of the body
(d) density of the body
Answer:
(c) weight of the body
Question 11.
The image shows the forces acting on a block. The length of the arrow shows the strength of the force and the direction of the arrow shows the direction of application of the force. What is the direction of the resultant force?
(a) Upwards
(b) Downwards
(c) Towards left
(d) Towards right
Answer:
(d) Towards right
Question 12.
A force of 10 N is acting on a block towards the left, if the force of 15 N is acting towards the right. How much net force is acting on the object?
(a) 5 N towards left
(b) 5 N towards right
(c) 25 N towards left
(d) 25 N towards right
Answer:
(b) 5 N towards right
Question 13.
A block is at rest on a table. A girl applies a force towards the right. The applied force is equal to the frictional force between block and the surface. What will happen to the block?
(a) It starts rotating
(b) It does not move
(c) It will start sliding towards left
(d) It will start sliding towards right
Answer:
(b) It does not move
Question 14.
Two boys X and Y push a block in directions shown in the image. If the box starts moving towards the left, what will be the direction of the frictional force acting on the block?
(a) Downward to the ground
(b) Upwards towards the block
(c) Opposite to the force applied by X
(d) Opposite to the force applied by Y
Answer:
(c) Opposite to the force applied by X
Question 15.
Which of the given example can be illustrated using the Newton’s first law of motion?
(a) Rowing of boat
(b) Rocket propulsion
(c) Wearing a seat belt in a car
(d) Releasing an arrow from bow
Answer:
(c) Wearing a seat belt in a car
Question 16.
A ball of 150 g is hit with a bat; the ball starts travelling with a velocity of 3m/s. What is the momentum of the ball?
(a) 0.05 kg m/s
(b) 0.45 kg m/s
(c) 50 kg m/s
(d) 450 kg m/s
Answer:
(b) 0.45 kg m/s
Question 17.
A marble of mass “m” at rest is pushed with force “F”, it starts travelling with velocity “y” in time “t”. Which option correctly relates the force with change in momentum?
(a) F= (mv.t)
(b) F= (mv/t)
(c) F=(mg.t)
(d) F=(mG/t)
Answer:
(b) F= (mv/t)
Question 18.
The image shows the forces acting on the car. Which option defines the state of the car?
(a) Car is at rest
(b) Car is accelerating
(c) Car is slowing down
(d) Car is moving with a constant velocity
Answer:
(d) Car is moving with a constant velocity
Question 19.
According to the third law of motion, every object acted upon by an external force applies an equal force in opposite direction. Which of the following phenomenon is best described by this law?
(a) Recoil when a gun is fired
(b) Engine thrust produced by rockets
(c) An apple kept on the desk motionless
(d) All of the above
Answer:
(d) All of the above
Question 20.
The inertia of an object tends to cause the object:
(a) to increase its speed
(b) to decrease its speed
(c) to resist any change in its state of motion
(d) to decelerate due to friction
Answer:
(c) to resist any change in its state of motion
Question 21.
A passenger in a moving train tosses a coin, which falls behind him. It means that motion
(a) accelerated
(b) uniform
(c) retarted
(d) along circular tracks
Answer:
(a) accelerated
Question 22.
Newton’s first law introduces the concept of …………………… .
(a) Momentum
(b) Inertia
(c) Conservation of energy.
(d) Action and reaction.
Answer:
(b) Inertia
Question 23.
According to the third law of motion, action and reaction:
(a) Always act on the same body.
(b) Always act on different bodies in opposite directions.
(c) have same magnitude and directions.
(d) Act on either body at normal to each other.
Answer:
(b) Always act on different bodies in opposite directions.
Question 24.
A goalkeeper in a game of football pulls his hands backwards after holding the ball shot at the goal. This enables the goalkeeper to:
(a) exerts large force on the ball
(b) reduces the force exerted by the ball on hands.
(c) Increase the rate of change of momentum.
(d) Decrease the rate of change of momentum.
Answer:
(b) Reduce the force exerted by the ball on hands.
Question 25.
Swimming is possible by the:
(a) first law of motion
(b) second law of motion
(c) third law of motion
(d) Newton’s law of gravitation
Answer:
(c) third law of motion
Question 26.
The SI unit of force is
(a) newton per second
(b) newton-metre
(c) newton per square metre
(d) newton
Answer:
(d) newton
Question 27.
Action-reaction forces act:
(a) along different lines
(b) on different bodies
(c) in the same direction
(d) along different lines
Answer:
(b) on different bodies
Question 28.
A body is accelerating in a straight line. The unbalanced force acts
(a) In a direction opposite to the direction of motion.
(b) In the direction of motion of the body.
(c) In a direction perpendicular to the direction of motion of the body.
(d) none of the above
Answer:
(b) In the direction of motion of the body.
Question 29.
A spring balance A is suspended vertically from a rigid support. Another spring balance B is suspended from the hook of A. Now, a weight of 1 kg is suspended from the hook of B. The readings of balances A and B would be
(a) \(\frac{1}{2}\) kg each
(b) 1 kg each
(c) 2 kg each
(d) none of the above
Answer:
(b) 1 kg each
Question 30.
Newton’s second law of motion gives us
(a) definition of force
(b) definition of inertia
(c) measure of force
(d) measure of momentum
Answer:
(c) measure of force
How Forces Affect Motion Class 9 Assertion Reason Questions
I. Directions (Q. No. 1 to 14): Each question below consists of an Assertion (A) and a Reason (R).
Use the following key to choose the appropriate answer.
(a) Both A and R are true, but R is not the correct explanation of A.
(b) Both A and R are true, and R is the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Question 1.
Assertion (A): A magnet can exert a force on another magnet without being in contact with it.
Reason (R): Contact force comes into play only when two objects are in contact with each other.
Answer:
(a) Both A and R are true, but R is not the correct explanation of A.
Question 2.
Assertion (A): A positively charged body attracts another positively charged body.
Reason (R): Objects fall towards the Earth because it pulls them.
Answer:
(d) A is false but R is true.
Question 3.
Assertion (A): The frictional force in air and water depends on the shape of the object.
Reason (R): Objects are designed in special shapes to reduce friction.
Answer:
(b) Both A and R are true, and R is the correct explanation of A.
Question 4.
Assertion: If the net external force on a body is zero, then its acceleration is zero.
Reason: Acceleration does not depend on force.
Answer:
(c) A is true but R is false.
Question 5.
Assertion: A rocket works on the principle of conservation of linear momentum.
Reason: For a two-body system, when there is a change in momentum of one body, the same change occurs in the momentum of the second body but in the opposite direction.
Answer:
(b) Both A and R are true, but R is not the correct explanation of A.
Question 6.
Assertion: A quick collision between two bodies is more violent than a slow collision, even when the initial and the final velocities are identical.
Reason: The rate of change of momentum, which determines the force, is greater in the first case.
Answer:
(a) Both A and R are true, and R is the correct explanation of A.
Question 7.
Assertion: Linear momentum is conserved in both elastic and inelastic collisions.
Reason: Total energy is conserved in all collisions.
Answer:
(a) Both A and R are true, and R is the correct explanation of A.
Question 8.
Assertion: Force required to accelerate a mass in two perpendicular directions is never same.
Reason: The presence of g will not influence the acceleration.
Answer:
(c) A is true but R is false.
Question 9.
Assertion: While walking on ice, one should take small steps to avoid slipping.
Reason: This is because smaller steps ensure smaller friction.
Answer:
(c) A is true but R is false.
Question 10.
Assertion: A body is momentarily at rest when it reverses the direction.
Reason: A body cannot have acceleration if its velocity is zero at a given instant of time.
Answer:
(c) A is true but R is false.
Question 11.
Assertion: When a bullet is fired from a gun, there is a forward force on the bullet and recoil of gun.
Reason: Every action has an equal and opposite reaction.
Answer:
(b) Both A and R are true, but R is not the correct explanation of A.
Question 12.
Assertion: When we sit on a chair, our body exerts a force downward, and that chair needs to exert an equal force upward, or the chair will collapse.
Reason: The third law says that for every action, there is an equal and opposite reaction.
Answer:
(b) Both A and R are true, but R is not the correct explanation of A.
Question 13.
Assertion: Force exerted by the ground on the man moves him forward.
Reason: It is a reactional force.
Answer:
(a) Both A and R are true, and R is the correct explanation of A.
Question 14.
Assertion: Mass is a measure of inertia of the body in linear motion.
Reason: Greater the mass, greater is the force required to change its state of rest or motion.
Answer:
(b) Both A and R are true, but R is not the correct explanation of A.
II. Direction: (Q. No. 1 to 12): The questions given below contain –
Statement-I (Assertion-A) and Statement-2 (Reason-R). Each question has four options, (a), (b), (c), and (d), out of which only one is correct. Choose the correct option as under:
(a) Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation. of Assertion (A).
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false but Reason (R) is true.
Question 1.
Assertion (A): A back-seater moves forward when a fast-moving bike is stopped suddenly.
Reason (R): As driver applies the brakes suddenly, the lower part of the back seater’s comes to rest while the upper part continues to be in motion.
Answer:
(a) Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation. of Assertion (A).
Question 2.
Assertion (A): The tendency of undisturbed objects to stay at rest or to keep moving with the same velocity is called inertia.
Reason (R): The mass of an object is a measure of its inertia.
Answer:
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
Question 3.
Assertion (A): In balanced force net force is zero.
Reason (R): In balanced force equal force is acting on an object in two opposite direction.
Answer:
(a) Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation. of Assertion (A).
Question 4.
Assertion (A): Action and reaction do not cancel each other.
Reason (R): Action and reaction act simultaneously but on different objects.
Answer:
(a) Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation. of Assertion (A).
Question 5.
Assertion (A): It is easier to push an empty box than a box full of books.
Reason (R): Box full of books has less inertia than the empty box.
Answer:
(c) Assertion (A) is true, but Reason (R) is false.
Question 6.
Assertion (A): If we kick a football, it flies away.
Reason (R): If we kick a stone of the same size with equal force, it hardly moves.
Answer:
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
Question 7.
Assertion (A): All bodies have the same inertia.
Reason (R): Heavier or more massive objects offer larger inertia.
Answer:
(d) Assertion (A) is false, but Reason (R) is true.
Question 8.
Assertion (A): A person is hit harder when the person falls on a hard floor than when he falls on sand or cotton.
Reason (R): On hard surface, the person is brought to rest in a very short time, whereas on a heap of sand or cotton, he is brought to rest in a long time.
Answer:
(a) Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation. of Assertion (A).
Question 9.
Assertion (A): A gunman gets jerk in backward direction while firing a gun. When a bullet is fired from the gun
Reason (R): When a bullet is fired from the gun, it moves forward with greater velocity, but it exerts equal and opposite force backward.
Answer:
(a) Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation. of Assertion (A).
Question 10.
Assertion (A): It is easier to push an empty box than to push the box full of books.
Reason (R): An empty box has less inertia.
Answer:
(a) Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation. of Assertion (A).
Question 11.
Assertion (A): In the case of balanced force, the net effect caused to state of rest or motion is zero.
Reason (R): Balanced force can change the shape and rest or motion state of an object.
Answer:
(c) Assertion (A) is true but Reason (R) is false.
Question 12.
Assertion (A): In unbalanced forces, net resultant force is zero.
Reason (R): Unbalanced forces cause change in the state of rest or uniform motion along a straight line of the object.
Answer:
(d) Assertion (A) is false, but Reason (R) is true.
How Forces Affect Motion Class 9 Fill in the blanks
1. If the net force acting on an object is zero, the object will either remain at rest or move with …………………. .
Answer:
uniform velocity
2. When a moving bus suddenly stops, passengers fall forward due to the inertia of …………………… .
Answer:
motion
3. If two forces of 10 N act in opposite directions on an object, the net force is ………………….. so the object will not accelerate.
Answer:
zero
4. When you walk, you push the ground backward, and the ground pushes you forward due to …………………… law of motion.
Answer:
Newton’s Third
5. Friction is necessary for walking, but it also causes loss of energy in the form of ………………………. .
Answer:
heat
6. In a system of objects, internal forces cancel out, so only …………………………. forces affect the motion of the system.
Answer:
external
7. The SI unit of mass is …………………. .
Answer:
kilogram (kg).
8. The SI unit of force is …………………….. .
Answer:
kg ms-2
9. The tendency of undisturbed objects to stay at rest or to keep moving with the same velocity is called ………………. .
Answer:
inertia
10. One …………………… force is defined as the amount of force which produces an acceleration of 1 m/s2 in an object of 1 kg mass.
Answer:
newton
11. Every action has …………………….. and ………………………. reaction.
Answer:
equal, opposite
12. The mass of an object is a measure of its ……………………. .
Answer:
inertia.
13. Force of friction always ………………………. motion of objects.
Answer:
opposes.
How Forces Affect Motion Class 9 True or False
1. Weight and mass are measured in the same unit.
Answer:
False
2. The stretch in a spring remains the same regardless of the object’s weight.
Answer:
False
3. To move an object faster, it has to be pushed or pulled repeatedly.
Answer:
True
4. Frictional force acts only on solid surfaces.
Answer:
False
How Forces Affect Motion Class 9 Match the Following
Question 1.
Match the items in column A with those in column B.
| Column A | Column B |
| (i) Force | (p) Non-contact force |
| (ii) Digestion | (q) Measuring force |
| (iii) Force of gravity | (r) Push or pull |
| (iv) Friction force | (s) Muscular force |
| (v) Spring balance | (t) Contact force |
Answer:
(i) – (r), (ii) – (s), (iii) – (p), (iv) – (t), (v) – (q)
| Column A | Column B |
| (i) Force | (r) Push or pull |
| (ii) Digestion | (s) Muscular force |
| (iii) Force of gravity | (p) Non-contact force |
| (iv) Friction force | (t) Contact force |
| (v) Spring balance | (q) Measuring force |
Question 2.
Match the physical quantities with their SI units:
| Column A | Column B |
| (i) Force | (p) Meter per second squared (m/s2) |
| (ii) Mass | (q) Newton (N) |
| (iii) Acceleration | (r) Kilogram meter per second (kgm/s) |
| (iv) Momentum | (s) Kilogram (kg) |
(a) (i) – (r), (ii) – (s), (iii) – (q), (iv) – (p)
(b) (i) – (p), (ii) – (r), (iii) – (s), (iv) – (q)
(c) (i) – (q), (ii) – (p), (iii) – (r), (iv) – (s)
(d) (i) – (q), (ii) – (s), (iii) – (p), (iv) – (r)
Answer:
(d) (i) – (q), (ii) – (s), (iii) – (p), (iv) – (r)
| Column A | Column B |
| (i) Force | (q) Newton (N) |
| (ii) Mass | (s) Kilogram (kg) |
| (iii) Acceleration | (p) Meter per second squared (m/s2) |
| (iv) Momentum | (r) Kilogram meter per second (kgm/s) |
Question 3.
Match the effects of force with their examples:
| Column A | Column B |
| (i) Change in motion | (p) A person pedalling harder to move a bicycle faster |
| (ii) Change in shape | (q) A player deflecting a ball |
| (iii) Change in direction | (r) A rubber ball gets compressed when squeezed |
| (iv) Overcoming friction | (s) A football starts moving when kicked |
(a) (i) – (r), (ii) – (p), (iii) – (s), (iv) – (q)
(b) (i) – (s), (ii) – (r), (iii) – (q), (iv) – (p)
(c) (i) – (q), (ii) – (s), (iii) – (p), (iv) – (r)
(d) (i) – (p), (ii) – (q), (iii) – (r), (iv) – (s)
Answer:
(b) (i) – (s), (ii) – (r), (iii) – (q), (iv) – (p)
| Column A | Column B |
| (i) Change in motion | (s) A football starts moving when kicked |
| (ii) Change in shape | (r) A rubber ball gets compressed when squeezed |
| (iii) Change in direction | (q) A player deflecting a ball |
| (iv) Overcoming friction | (p) A person pedalling harder to move a bicycle faster |
Question 4.
Match the concepts with their explanations:
| Column A | Column B |
| (i) Inertia | (p) Change in momentum over time |
| (ii) Momentum | (q) Resistance to change in motion |
| (iii) Impulse | (r) Product of mass and velocity |
| (iv) Friction | (s) Force that opposes motion |
(a) (i) – (r), (ii) – (p), (iii) – (s), (iv) – (q)
(b) (i) – (p), (ii) – (q), (iii) – (r), (iv) – (s)
(c) (i) – (q), (ii) – (s), (iii) – (p), (iv) – (r)
(d) (i) – (s), (ii) – (r), (iii) – (q), (iv) – (p)
Answer:
(c) (i) – (q), (ii) – (s), (iii) – (p), (iv) – (r)
| Column A | Column B |
| (i) Inertia | (q) Resistance to change in motion |
| (ii) Momentum | (s) Force that opposes motion |
| (iii) Impulse | (p) Change in momentum over time |
| (iv) Friction | (r) Product of mass and velocity |
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