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Class 9 Science MCQ Questions of Force and Laws of Motion with Answers?

Answer 1

You can peruse all of the Class 9 Science MCQ Questions of Force and Laws of Motion with Answers and attempt them at whatever point it may suit you. MCQ Questions of Force and Laws of Motion are set up to cover every one of the key concepts associated with the chapters. To know the significant topics, key ideas, and concepts from the part which can be tried in the test in the objective-type questions.

Students should practice all of these questions to score great marks in the exams. Every one of the questions is provided with the right answers. Learn MCQ Questions for Class 9 Science with answers that help to clear your school exams. 

Practice MCQ Questions for class 9 Chapter-Wise

1. 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

2. A goalkeeper in a game of football pulls his hands backward after holding the ball shot at the goal. This enables the goalkeeper to

(a) exert larger force on the ball
(b) reduce the force exerted by the balls on the hands
(c) increase the rate of change of momentum
(d) decrease the rate of change of momentum

3. 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

4. A passenger in a moving train tosses a coin that falls behind him. It means that the motion of the train is

(a) accelerated
(b) uniform
(c) retarded
(d) along circular tracks

5. Rocket works on the principle of conservation of

(a) mass
(b) energy
(c) momentum
(d) velocity

6. When a car at high speed makes a sharp turn, the driver in a car tends to get thrown to the side opposite to the turn. This is due to the

(a) inertia of motion
(b) inertia of time
(c) inertia of rest
(d) inertia of direction

7. An athlete does not come to rest immediately after crossing the winning line due to the

(a) inertia of motion
(b) inertia of rest
(c) inertia of direction
(d) none of these

8. If the force acting on the body is zero. Its momentum is:

(a) Zero
(b) Constant
(c) Infinite
(d) None of the above

9. Force is defined as

(a) change in momentum
(b) rate of change of momentum
(c) the quantity that opposes inertia
(d) the quantity that keeps the velocity constant

10. In high jump competition, the athlete is made to fall on a cushioned bed to:

(a) To decrease his momentum fast
(b) Make him stop quickly
(c) Increase the time to stop
(d) Make him sleep comfortably

11. .................. is a force, which always opposes the motion of one body over the other body in contact with it

(a) Gravitational force
(b) Reaction force
(c) Normal force
(d) Frictional force

12. In the following example, try to identify the number of times the velocity of ball changes - A football player kicks a football to another player of his team who kicks the football towards the goal. The goalkeeper of the opposite team collects the football and kicks it towards a player of his own team.

(a) Three times
(b) Five times
(c) Four times
(d) Six times

13. An object will continue to accelerate until the

(a) Resultant force on it is zero
(b) The velocity changes direction
(c) Resultant force on it is increased continuously
(d) Resultant force begins to decrease

14.  If a bus starts suddenly, the passengers in the bus will tend to fall

(a) In the direction opposite to the direction of motion of the bus.
(b) In the same direction as the direction of motion of the bus.
(c) Sideways.
(d) None of the above.

15. When a force is exerted on an object, it can change its:

(a) State
(b) Position
(c) Shape
(d) All the above

16. When unbalanced forces act on a body, the body:

(a) Must move with uniform velocity
(b) Must remain at rest
(c) Must experience acceleration
(d) Must move in a curved path

17. A wooden block of mass 20 kg accelerates at the rate of 4 m/s².  Calculate the applied force on the block.

(a) 20 N
(b) 40 N
(c) 70 N
(d) 80 N

18. A water tank filled up to 2/3 of its height is moving at a uniform speed. On sudden application of the brake, the water in the tank would

(a) Move backward
(b) Move forward
(c) Come to the rest
(d) Be unaffected

19. When a balloon held between the hands is pressed, its shape changes. This happens because:

(a) Balanced forces act on the balloon
(b) Unbalanced forces act on the balloon
(c) Frictional forces act on the balloon
(d) Gravitational force acts on the balloon

20. A real gas at a very high pressure occupies

(a) Less volume than that of an ideal gas under identical condition
(b) More volume than that of an ideal gas under identical conditions
(c) Same volume as that of an ideal gas under identical conditions
(d) Cannot be predicted

Answer 2

 1. Answer : (b) always act on different bodies in opposite directions

Explanation: As per Newton's third law, whenever one object exerts a force on another object, the second object exerts an equal and opposite on the first. If object A exerts a force on object B, object B also exerts an equal and opposite force on object A.

2. Answer :  (d) decrease the rate of change of momentum

Explanation: A goalkeeper in a game of football pulls his hands backward after holding the ball shot at the goal. This enables the goalkeeper to decrease the rate of change of momentum and hence reduce the force exerted by the ball on hands.

3. Answer : (c) to resist any change in its state of motion

Explanation: Inertia is the physical property of a body of an object that tends to cause the object to resist any change in its state of rest or motion. The object will stay at rest if it is at rest or will stay in motion if the object is already in motion.

4. Answer :  (a) accelerated

Explanation: A passenger in a moving train tosses a coin upward which falls behind him. It implies that the motion of the train is accelerated. It happens because by the time the coin remains in the air, its velocity reduces and it falls behind the passenger.

5. Answer :  (c) momentum

Explanation: The rocket works because of the law of conservation of linear momentum. The law of conservation of linear momentum is very important in physics. Momentum is defined as the mass of object times its velocity.

6. Answer :  (a) inertia of motion

Explanation: It is because the body of the passengers tries for resisting the change exactly in the side of inertia. Hence, the passengers will slip for getting to one side of a car. When a motor makes a sharp turn at a high speed we tend to get thrown to one side due to the inertia of motion.

7. Answer :  (a) inertia of motion

Explanation: Inertia is a habit of an object to resist any change in its state of motion. In case of a running athlete, the body is in motion but when the athlete stop immediately then his legs will come to rest while a body is in moving forward.

8. Answer :  (b) Constant

Explanation: The relationship also implies the conservation of momentum: when the net force on the body is zero, the momentum of the body is constant. Any net force is equal to the rate of change of momentum.

9. Answer :  (b) rate of change of momentum

Explanation: Newton actually stated his second law of motion in terms of momentum: The net external force equals the change in momentum of a system divided by the time over which it changes. The change in momentum is the difference between the final and initial values of momentum.

10. Answer :  (c) Increase the time to stop

Explanation: This is done to prevent injury to the athlete when he falls down after making a high jump. When the high jumper falls on a soft landing site, such as a cushion or a heap of sand, Then the jumper takes a longer time to come to a stop. Thus cushion or sand, being soft reduces the athlete's Momentum more gently.

11. Answer :   (d) Frictional force

Explanation: The property by virtue of which a resisting force is created between two rough bodies that resist the sliding of one body over the other is known as friction. The force that always opposes the motion of one body over the other body in contact with it is known as the force of friction or frictional force.

12. Answer : (c) Four times

Explanation:  The velocity of football changes four times. First, when a football player kicks to another player, second when that player kicks the football to the goalkeeper. Third when the goalkeeper stops the football. Fourth when the goalkeeper kicks the football towards a player of his own team.

13. Answer :  (a) Resultant force on it is zero

Explanation: The mass of the object is constant and cannot be zero. So, we can say an object will continue accelerating until the resultant force on it is zero.

14.  Answer :  (a) In the direction opposite to the direction of motion of the bus.

Explanation: The passengers in a bus tend to fall back when it starts suddenly due to inertia as the passengers tend to remain in a state of rest while the bus starts to move.

15. Answer :  (d) All the above

Explanation:  When a force is exerted on an object, it can change its state, position, and also its shape.

16. Answer :  (c) Must experience acceleration

Explanation: The Second Law of Motion states that if an unbalanced force acts on a body, that body will experience acceleration ( or deceleration), that is, a change of speed. One can say that a body at rest is considered to have zero speed, ( a constant speed). So any force that causes a body to move is an unbalanced force.

17. Answer :  (d) 80 N

Explanation:  Mass = 20 kg, Acceleration = 4 m/s².

According to the second law of motion,

Force = mass \(\times\) acceleration

F = 20 \(\times\) 4

F = 80 N

18. Answer :  (b) Move forward

Explanation: A water tanker filled up to 2/3 of its height is moving at a uniform speed. On sudden application of the brake, the water in the tank would. On sudden application of brakes, water in the tank would move forward due to inertia of motion.

19. Answer :  (a) Balanced forces act on the balloon

Explanation: Balanced forces are responsible for bringing about a change in the shape of an object.

20.  Answer :  (b) More volume than that of an ideal gas under identical conditions

Explanation: When there is high pressure, the distance between the adjacent gas molecules is relatively less. As a result, it occupies a higher volume as compared to an ideal gas subjected to high pressure due to the absence of repulsion force. 

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