Two identical balls are approaching towards each other on a straight line with velocity `2m//s` and `4m//s`, respectiely. Find the final velocities after elastic collision between them.

Explanation

Resolving the velocity before impact, velocity component along the plane `=8sin60^(@)=4sqrt(3) m//s` and that normal to the plane =`8cos60^(@)=4m//s`.
If `v m//s` is the velocity after the impact and `theta` the angle made by the velocity with the normal to the plane, then velocity component along the plane `=vsintheta` and that normal to the plane `=v costheta`.
As the velocity along the plane remains uchanged,
`:. vsintheta=4sqrt(3)`.............i
Fom Newton's expereimental law,
`costheta=e(4)` (in magnitude)
`=2 `................ii
squaring and adding eqn i and ii
`v^(2)=52impliesv=2sqrt(13)m//s`
`dividing eqn i by eqn ii we get