Question

A ball with a mass of `3 kg` is rolling at `25 m/s` and elastically collides with a resting ball with a mass of `2 kg`. What are the post-collision velocities of the balls?

Answer 1

`v_1^'=5" " m/s`
`v=2^'=30" " m/s`

Explanation:

`m_1*v_1+0=m_1*v_2^'+m_2*v_2^' " Conversation of momentum"`
`3*25+0=3*v_1^'+2*v_2^'`
`75=3*v_1^'+2*v_2^' " "(1)`
`v_1+v_1^'=v_2+v_2^'" "(2)`
`25+v_1^'=0+v_2^'" "v_2^'=25+v_1^'" "(3)`
`75=3*v_1^'+2(25+v_1^')`
`75=3*v_1^'+50+2v_1^'`
`75-50=5v_1^' " "25=5v_1^'" "v_1^'=5" " m/s`
`use (3):`
`v_2^'=25+5`
`v=2^'=30" " m/s`