For a relation F = $\dfrac{m(Δv)}{Δt}$, to hold true, the condition(s) necessary is/are:

1. velocities are equal to the velocity of light
2. velocities are much smaller than the velocity of light
3. mass remains constant
4. both (b) and (c)

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.