two smooth spheres of masses 2kg and 4kg collide obliquely . the 2 kg mass is brought to rest. the coefficient of restitution is $\displaystyle 1/2 $

prove before the impact the spheres were moving in perpendicular directions to each other.

using conservation of momentum. $\displaystyle 4x+2y=4p+2(0) $ where x and y are velocities before impact. p is velocity after impact of 4kg

newtons experimental law $\displaystyle p-0/x-y =-1/2 $

once i get there velocities in terms of the variables i dont know what to do