Two balls of masses 4m and 8m are in motion with velocities 2v and v respectively. The ratio of their momentum would be :

1. 2 : 1
2. 1 : 2
3. 1 : 1
4. 1 : 4

A body of mass m moving with a velocity v is acted upon by a force. Write expression for change in momentum in each of the following cases (i) when v << c (ii) when v → c, and (iii) when v << c but m does not remain constant. Here c is the speed of light.

Two bodies A and B of same mass are moving with velocities v and 2v respectively.
Compare (i) their inertia (ii) their momentum.