Selina Solutions Class 9 Physics Solutions for Exercise 3C in Chapter 3 - Chapter 3 Laws Of Motion

Question 6 Exercise 3C

Two balls A and B of masses m and 2m are in motion with velocities 2v and v respectively. Compare (i) their inertia, (ii) their momentum, and (iii) the force needed to stop them in same time.


(i) Comparing inertia of two bodies A and B;

The inertia of body A: Inertia of body B :: m:2m or 1:2

(ii) Comparing the momentum of both bodies

Momentum of body A = m(2v) = 2mv

Momentum of body B = (2m)v= 2mv

The momentum of body A: Momentum of body B :: 2mv:2mv or 1:1

(iii) Comparing the force needed to stop both the bodies at the same time

Rate of momentum change is directly proportional to the force applied on a body as per

Newton’s second law of motion. Hence;

The force required to stop A: Force required to stop B:: 1:1

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