A `1 kg` ball moving at `12 m//s` collides head on with a `2g` ball moving in the opposite direction at `24 m//s`. The velocity of each ball after the impact, if the coefficient of restitution is `2//3` is

Options

A. `12 m//s , 36 m//s`
B. `-28 m//s , -4 m//s`
C. `20 m//s , 24 m//s`
D. `-20 m//s , -4 m//s`

Answer

B

Explanation

`vecv_(1) =((m_(1)-em_(2))/(m_(1)+m_(2))) vecu_(1) + ((m_(2)(1+e))/(m_(1)+m_(2)))vec u_(2)`
`vec v_(2) = ((m_(1)(1+e))/(m_(1)+m_(2))) vecu_(1) + ((m_(2) -em_(1))/(m_(1) +m_(2))) vec u_(2)`.