Question

A ball with a mass of `5 kg` is rolling at `6 m/s` and elastically collides with a resting ball with a mass of `9 kg`. What are the post-collision velocities of the balls?

Answer 1

`v_1=-12/7 m/s`
`v_2=30/7m/s`

Explanation:

`5*6+0=5*v_1+9*v_2" Conversation of momentum"`
`30=5*v_1+9*v_2 " (1)"`
`6+v_1=0+v_2`
`"'the sum of velocities of objects before and after collision is equal'"`
`v_2=6+v_1" (2)"`
`30=5*v_1+9*(6+v_1)`
`30=5*v_1+54+9*v_1`
`30-54=14*v_1`
`-24=14*v_1`
`v_1=-24/14`
`v_1=-12/7 m/s`
`"use (2)"`
`v_2=6-12/7`
`v_2=30/7m/s`