Question

A ball with a mass of `3 kg` is rolling at `11 m/s` and elastically collides with a resting ball with a mass of `4 kg`. What are the post-collision velocities of the balls?

Answer 1

`"see to animation"`
`v_r=-11/7 m/s`
`v_y=66/7 m/s`

Explanation:

`m_r:" mass of the red ball"`
`m_y:" mass of the yellow ball"`
`v_r:" velocity of the red ball after collision"`
`v_y:" velocity of the yellow ball after collision"`
`3*11+0=3*v_r+4*v_y`
`33=3*v_r+4*v_y" (1)"`
`11+v_r=0+v_y" (2)"`
`v_y=11+v_r" (3)"`
`"insert (3) into (2)"`
`33=3*v_r+4*(11+v_r)`
`33=3*v_r+44+4*v_r`
`33-44=7*v_r`
`-11=7*v_r`
`v_r=-11/7 m/s`
`"use (3):"`
`v_y=11-11/7`
`v_y=66/7 m/s`