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Violagirl
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Homework Statement
A billiard ball strikes an identical billiard ball initially at rest and is deflected 45 degrees from its original position. Show that if the collision is elastic, the other ball must move at 90 degrees to the first and with the same speed.
Homework Equations
Momentum:
mv = m1v1 + m2v2
Kinetic energy = 1/2m1v12 =1/2m1v12 + m2v22
The Attempt at a Solution
I think I've come up with three equations so far in breaking the problem up but I have no idea if I'm the right track or not. Any input is much appreciated.
1. Pfx=Pix
vxcos 45° + m2vxcos θ = v0
2. Pfy=Piy
vysin 45° - vysin θ = 0
vysin 45°=vysin θ
3. 1/2v02 = v12+v22