Question

A ball of mass $40g$ moving at a speed of $3m/s$ hits a stationary ball of mass $20g$. If the $20g$ ball starts moving with a speed of $2m/s$, what would be the speed of the $40g$ ball?

Answer 1

By momentum conservation,

Velocity of $20g$ block=$\frac{2\times 40}{40\times 20}$

Velocity of $40g$ block=V=$\frac{2\times 60}{80}=\frac{12}{8}=\frac{3}{2}=1.5$m/s