Chapter 9 – Force and Laws of Motion – Ankit Enterprises

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) Exert large force on the ball
(b) Increases the force exerted by the ball on hands
(c) Increase the rate of change of momentum
(d) Decrease the rate of change of momentum

An object of mass 2 kg is sliding with a constant velocity of 4 m/s on a friction less horizontal table. The force required to keep the object moving with the same velocity is:

(a) 32 N
(b) 0 N
(c) 2 N
(d) 8 N

Newton’s third law of motion explains the two forces namely ‘action’ and ‘reaction’ coming into action when the two bodies are in contact with each other. These two forces:

(a) Always act on the same body
(b) Always act on the different bodies in opposite directions
(c) Have same magnitude and direction
(d) Acts on either body at normal to each other

In a rocket, a large volume of gases produced by the combustion of fuel is allowed to escape through its tail nozzle in the downward direction with the tremendous speed and makes the rocket to move upward.

Which principle is followed in this take off of the rocket?

(a) Moment of inertia
(b) Conservation of momentum
(c) Newton’s third law of motion
(d) Newton’s law of gravitation

A water tank filled upto 2/3 of its height is moving with 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

Velocity versus time graph of a ball of mass 50 g rolling on a concrete floor is shown in the figure below. What will be the frictional force of the floor on the ball?

(a) 0.5 N
(b) 50 N
(c) 5 N
(d) 0.05 N

The seat belts are provided in the cars so that if the car stops suddenly due to an emergency braking, the persons sitting on the front seats are not thrown forward violently and saved from getting injured. Can you guess the law due to which a person falls in forward direction on the sudden stopping of the car?

(a) Newton’s first law of motion
(b) Newton’s second law of motion
(c) Newton’s third law of motion
(d) Newton’s law of gravitation

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

Which of the following situations involves the Newton’s second law of motion?

(a) A force can stop a lighter vehicle as well as a heavier vehicle which are moving
(b) A force exerted by a lighter vehicle on collision with a heavier vehicle results in both the (vehicles coming to a standstill
(c) A force can accelerate a lighter vehicle more easily than a heavier vehicle which are moving
(d) A force exerted by the escaping air from a balloon in the downward direction makes the balloon to go upwards

The speed of a car weighing 1500 kg increases from 36 km/h to 72 km/h uniformly. What will be the change in momentum of the car?

(a) 15000 kg km/h
(b) 15000 kg m/s
(c) 54000 kg m/s
(d) 54000 g m/s

A passenger in a moving train tosses a coin which falls behind him. Observing this statement what can you say about the motion of the train?

(a) Accelerated
(b) Retarded
(c) Along circular tracks
(d) Uniform

Newton’s first law of motion says that a moving body should continue to move forever , unless some external forces act on it. But a moving cycle comes to rest after some time if we stop pedaling it. Can you choose the correct reason for the stoppage of cycle?
i. Air resistance
ii. Gravitational pull of the earth
iii. Friction of the road
iv. Heat of the environment

(a) (iii) and (iv)
(b) (i) and (iii)
(c) (i) and (ii)
(d) (ii) and (iii)

A man wearing a bullet-proof vest stands on roller skates. The total mass is 80 kg. A bullet of mass 20 g is fired at 400 m/s. It is stopped by the vest and falls to the ground. What is then the velocity of the man?

(a) 1 m/s
(b) 0.1 m/s
(c) 0.01 m/s
(d) 0 m/s

The unit of measuring the momentum of a moving body is:

(a) m/s
(b) kg.m/s
(c) kg.m/s2
(d) N m2/kg2

The inertia of a moving object depends on:

(a) (i) and (ii)
(b) only (i)
(c) only (ii)
(d) (iii) and (iv)

Rocket works on the principle of conservation of:

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

Among the equal-sized stone and a football, the inertia will be higher of:

(a) football
(b) stone
(c) both
(d) none of them

A batsman hits a cricket ball which then rolls on the 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 on the ball opposing the motion.
(d) there is no unbalanced force on the ball so the ball would want to come to rest.

What is the momentum of an object of mass m, moving with a velocity v?

(a) (mv)2
(b) mv2
(c) \(\frac{1}{2}\) mv2
(d) mv

Friction is:

(a) useful to us
(b) harmful to us
(c) both useful as well as harmful to us
(d) none of them.

Fill in the blank

The SI unit of momentum is .

Fill in the blank

The natural tendency of objects to resist a change in their state of rest or of uniform motion is called

Fill in the blank

To every action, there is an and opposite reaction.

Fill in the blank

The resultant force of balanced forces is

Fill in the blank

The force can change the motion, direction, or of an object.

Fill in the blank

The value of inertia depends on the of an object.

Fill in the blank

The rate of change of momentum of an object is to the applied unbalanced force in the direction of the force.

Write the unit of pressure.

A body is moving with constant velocity, then what will be the acceleration of that body?

Write the S.I unit of force.

Chapter 9 – Force and Laws of Motion

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