Question

A ball with a mass of `6 kg` moving at `7 m/s` hits a still ball with a mass of `12 kg`. If the first ball stops moving, how fast is the second ball moving?

Answer 1

Use the conservation of momentum equation `m_1v_1=m_2v_2` to find that `v_2=(7/2 (m)/s)`

Explanation:

Remember the equation for momentum: `p=mv` (the `p` and `v` are both vector quantities, so should have little arrows on them).

Momentum is conserved between 2 bodies, or `m_1v_1=m_2v_2`. So when 1 ball hits another non-moving ball, how fast will the 2nd ball move after the collision - we can figure out using the conservation of momentum equation:

`m_1v_1=m_2v_2`

`(6kg)(7m/s)=(12kg)v_2`

And now we solve for `v_2`

`v_2=(7/2 (m)/s)`