Question

A ball with a mass of `12kg` moving at `4 m/s` hits a still ball with a mass of `2 kg`. If the first ball stops moving, how fast is the second ball moving?

Answer 1

`v_2=24ms^-1`

Explanation:

This is a simple case of conservation of linear momentum. This means that `m_1v_1=m_2v_2`.
Reason why is because they said that the first ball stops, so the velocity of the first ball after collision is `0` and that reduces our equation so.

We have, `m_1=12kg`, `m_2=2kg`, `v_1=4ms^-1`, so we have to find `v_2`.

So, `12*cancel{4}^2=cancel{2}^1*v_2`

I'm sure it gets simple from here.