Question

A ball of mass 3 kg and a ball of mass 2 kg roll towards each other on a flat surface. How far is the centre of mass from the 3 kg ball of the 2 balls are separated by 6 m?

(a) 1.2 m

(b) 2.4 m

(c) 3.6 m

(d) 4.8 m

This question was posed to me during a job interview.

The origin of the question is System of Particles topic in portion System of Particles and Rotational Motion of Physics – Class 11

Answer 1

Right answer is (b) 2.4 m

Explanation: Sum of masses = 3 + 2 = 5 kg

Centre of mass from 3 kg ball = (6 x 2) / 5

 = 2.4 m.