Laws of Motion MCQs for NEET

1 A ship of mass 3 X 107 kg initally at rest is pulled by a force of 5 X 104 N through a distance of 3m. Assume the resistance due to water is negligible , then the speed of the ship is

A 1 . 5 m/s

B 60 m/s

C 0 . 1 m/s

D 5 m/s

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Answer:0 . 1 m/s

2 A block of mass M is placed on a flat surface . A force is applied to move it parallel to the surface . The frictional force f developed is proportional to the

A square of the mass of the body

B mass of the body

C reciprocal of the mass of the body

D reciprocal of the square of the body

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Answer:mass of the body

3 A block of mass 2 kg rests on a rough inclined plane making an angle of 30 degree with the horizontal . The coefficient of static friction between he block and the plane is 0.7 . The frictional force on the block is

A 9.8 N

B 0.7 x 9.8 x √3 N

C 9.8 x √3 N

D 0.7 x 9.8 N

View Answer

Answer:0.7 x 9.8 N

4 A body is sliding down a rough inclined plane which makes an angle of 30 dreeg with the horizontall . If the coeffcient of friction is 0.26, the acceleration in m/s² is

A 1 . 95

B 2 . 78

C 3 . 47

D 4 . 6

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Answer:2 . 78

5 Two billiard balls A and B, each of mass 50g and moving in opposite directions with speed of 5m s^-1 each, collide and rebound with the same speed. If the collision lasts for 10^-3 s, which of the following statements are true?

A The impulse imparted to each ball is 0.25 kg m s^-1 and the force on each ball is 250 N.

B The impulse imparted to each ball is 0.25 kg m s^–1 and the force exerted on each ball is 25 × 10^–5 N.

C The impulse imparted to each ball is 0.5 Ns.

D The impulse and the force on each ball are equal in magnitude and opposite in direction.

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Answer:C, D

6 In Fig. below, a body A of mass m slides on plane inclined at angle θ1 to the horizontal and μ1 is the coefficient of friction between A and the plane. A is connected by a light string passing over a frictionless pulley to another body B, also of mass m, sliding on a frictionless plane inclined at angle θ2 to the horizontal. Which of the following statements are true?

Laws of motion

A A will never move up the plane.

B A will just start moving up the plane when
μ = sin θ₂ – sin θ₁ / cos θ₁

C For A to move up the plane, θ₂ must always be greater than θ₁

D B will always slide down with constant speed.

View Answer

Answer:B, C

7 Mass m₁ moves on a slope making an angle θ with the horizontal and is attached to mass m₂ by a string passing over a frictionless pulley as shown in Fig. 5.2. The co-efficient of friction between m₁ and the sloping surface is μ.

Laws of motion

Which of the following statements are true?

A If m₂ > m₁ sinθ , the body will move up the plane.

B If m₂ > m₁ sinθ + μ cosθ , the body will move up the plane.

C If m₂ < m₁ sinθ + μ cosθ , the body will move up the plane.

D If m₂ < m₁ sinθ − μ cosθ , the body will move down the plane.

View Answer

Answer:B, D

8 In Fig. 5.1, the co-efficient of friction between the floor and the body B is 0.1. The co-efficient of friction between the bodies B and A is 0.2. A force F is applied as shown on B. The mass of A is m/2 and of B is m. Which of the following statements are true?

Laws of motion

A The bodies will move together if F = 0.25 mg.

B The body A will slip with respect to B if F = 0.5 mg.

C The bodies will be at rest if F = 0.1 mg.

D The maximum value of F for which the two bodies will move together is 0.45 mg.

View Answer

Answer:All

9 The motion of a particle of mass m is given by x = 0 for t < 0 s, x( t ) = A sin 4p t for 0 < t <(1/4) s (A > o), and x = 0 for t >(1/4) s. Which of the following statements is true?

A The force at t = (1/8) s on the particle is –16π2 A m.

B The particle is acted upon by on impulse of magnitude 4π2 A m at t = 0 s and t = (1/4) s.

C The particle is not acted upon by any force.

D The particle is not acted upon by a constant force.

View Answer

Answer:A, B, D

10 A body of mass 2kg travels according to the law x(t ) = pt + qt² + rt³ where p = 3 ms^-1, q = 4 ms^-2 and r = 5 ms^-3. The force acting on the body at t = 2 seconds is

A 136 N

B 134 N

C 158 N

D 68 N

View Answer

Answer:136 N

11 A hockey player is moving northward and suddenly turns westward with the same speed to avoid an opponent. The force that acts on the player is

A frictional force along westward.

B muscle force along southward.

C frictional force along south-west.

D muscle force along south-west.

View Answer

Answer:frictional force along south-west.

12 Conservation of momentum in a collision between particles can be understood from

A conservation of energy.

B Newton’s first law only.

C Newton’s second law only.

D both Newton’s second and third law.

View Answer

Answer:both Newton’s second and third law.

13 In the previous problem (5.3), the magnitude of the momentum transferred during the hit is

A Zero

B 0.75 kg m s^–1

C 1.5 kg m s^–1

D 14 kg m s^–1

View Answer

Answer:1.5 kg m s^–1

14 A metre scale is moving with uniform velocity. This implies

A the force acting on the scale is zero, but a torque about the centre of mass can act on the scale.

B the force acting on the scale is zero and the torque acting about centre of mass of the scale is also zero.

C the total force acting on it need not be zero but the torque on it is zero.

D neither the force nor the torque need to be zero.

View Answer

Answer:the force acting on the scale is zero and the torque acting about centre of mass of the scale is also zero.

15 A ball is travelling with uniform translatory motion. This means that

A it is at rest.

B the path can be a straight line or circular and the ball travels with uniform speed.

C all parts of the ball have the same velocity (magnitude and direction) and the velocity is constant.

D the centre of the ball moves with constant velocity and the ball spins about its centre uniformly.

View Answer

Answer:all parts of the ball have the same velocity (magnitude and direction) and the velocity is constant.

16 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

View Answer

Answer:0.1 m/s

17 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

View Answer

Answer:Accelerated

18 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

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Answer:15000 kg m/s

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

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Answer:Balanced forces act on the balloon

20 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

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