Question

A body of mass 0.120 kg and a velocity of 0.50 m/s hits another identical body at rest, and the two recoils forming 90 degrees between them. If the final velocity of one of the balls are directed 30 degrees above horizontal, find their speeds after collision.

Answer 1

The speeds after collisions can be found by momentum conservation by axes:

$Ox:0.12·0.5=0.12v\cos30°+0.12·u\cos60°,\\ Oy: 0.12·0=0.12v\sin30°+0.12u\sin60°.\\ u=-0.5\text{ m/s},\\ v=0.87\text{ m/s}.$