Question

A ball with a mass of `9 kg` moving at `15 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=67,5 m/s`

Explanation:

`sum P_b=sum P_a` # " sum of momentums before event ,must be equal sum of momentums after event"#
`9*15+0=0+2*v`
`135=2*v`
`v=135/2`
`v=67,5 m/s`