# Elastic collision/ projectile motion

1. Nov 16, 2008

### rugbygirl2

I have a 4kg mass (m1) moving at 3m/s towards a 8kg mass (m2) at rest on a 2m long frictionless table that is of unknown height. I solved for the velocities after the collsion m1= 2m/s and m2= 1m/, suppose the two masses were placed so that they left the edges of the table in opposite directions at the same time, ie the collision happened so that m2 was placed 0.66667m from the edge. What is the distance that each travels from the base of the table (delta x).
I have
m1= 4kg, and a initial vx of 2 m/s
m2= 8kg, and a initial vx of 1 m/s
I do not know the height or time of flight so any way I substitute equations I get 2 unknowns. Any help or ideas would be appreciated!

2. Nov 16, 2008

### schroder

This probably belongs in the homework section. You should show how you calculated your velocities. Hint: The values may be correct, but recheck which velocity is for which mass, and be alert for a rebound after collision. Try using simultaneous equations involving the conservation of momentum and the conservation of energy.