Question

A ball with a mass of `2 kg` moving at `3 m/s` hits a still ball with a mass of `8 kg`. If the first ball stops moving, how fast is the second ball moving?

Answer 1

Momentum of the second ball + momentum of the first ball = constant.

Explanation:

Momentum of the first ball:
`m_1*v_1=2kg*3m//s=6kg*m//s`

This is completely transferred to the second ball:
`m_2*v_2=8kg*v_2m//s=6kg*m//s`

So `v_2=(6cancel(kg)*m//s)/(8cancel(kg))=0.75m//s`