1. ## collision

A smooth sphere P, of mass m kg, moving with speed 5u m/s collides directly with a smooth sphere Q, of mass 2m kg, moving towards each other with speed 2u m/s.
The coefficient of restitution between the spheres is e.
find the condition satisfied by e if the 2 spheres move in the same direction after the collision.

using the 2 normal equations i got their final speeds to be 3u-2ue and 3u-ue
because they move in the same direction i let 3u-2ue >0 and 3u-ue>0
solving these i get e<3 and e>3/2
the answer at the back of the book is e<1/14
i can go though my answer in more detail if you need it
thanks

2. ## Re: collision

any helping information at all?