10 QA on laws of motion | Learn Physics

10 question-answers on laws of motion

1.       A man weighing 80 kg is standing on a trolley weighing 320 kg. The trolley is resting on friction less horizontal rails. If the man starts walking on the trolley along the rails at speed 1 m/s, then after 4 sec, his displacement relative to ground will be:

(a)    5 m

(b)   4.8 m

(c)    3.2 m

(d)   3.0 m

Ans : ( c)

2.       A body is acted upon by a constant force, then it will have a uniform

(a)    Speed

(b)   Momentum

(c)    Velocity

(d)   Acceleration

Ans : (d)

3.       Two bodies A and B are thrown upwards simultaneously with the same velocity. If the mass of A is greater than that of B, then

(a)    A will go higher than B

(b)   B will go higher than  A

(c)    A and B will go to same height

(d)   Nothing can be predicted

Ans: ( c)

4.       A brick of mass 5 kg is given an upward acceleration of 0.30 ms^-2 by pulling the brick vertically upwards with the help of a rope. Then tension in in the rope will be?

(a)    40 N

(b)   47.5 N

(c)    50.5 N

(d)   55 N

Ans:(c)

5.       A body of weight W₁ is suspended from the ceiling of a room through a chain of weight W_2. The earth pulls the chain by a force equal to?

(a)    W₁

(b)   (W₁+ W₂)/2

(c)    (W₁+ W₂)

(d)   W₁×  W₂

              Ans: (c )

6.       A motor cycle and a car are moving on a horizontal road with the same velocity. If they are brought to rest by the application of brakes,  which provided equal  retarding forces , then

(a)    Motor cycle will stop at shorter distance

(b)   Car will stop at the same distance

(c)    Both will stop at the same distance

(d)   Nothing can be predicted

Ans: (c )

7.       A body of mass 40 gram is moving with a constant velocity of 20 ms^-1 on horizontal friction less table, The force acting on the body is?

(a)    39,200 dyne

(b)   160 dyne

(c)    80 dyne

(d)   Zero

Ans: (d)

 

8.       A car travelling at a speed of 30 kmh^-1 is brought to a halt in 8 m by applying brakes. If the same car is travelling at 60 km h^-1 , It can be brought to a half with the same breaking power in?

(a)    32 m

(b)   24 m

(c)    16 m

(d)   8 m

Ans: (a)

9.       There are three Newton’s laws of motion, namely first, second and third laws. We can derive

(a)    All the laws independent of each other

(b)   First and second laws from third law

(c)    Third and first law from second law

(d)   Second and third laws from the first law.

Ans: (c )

10.   Physical independence of force is a consequence of

(a)    Third law of motion

(b)   Second law of motion

(c)    First laws of motion

(d)   All of this laws

Ans: (c)