physics
posted by sam .
Consider a frictionless track as shown in the figure below. A block of mass m1 = 4.25 kg is released from A. It makes a head on elastic collision at B with a block of mass m2 = 10.0 kg that is initially at rest. Calculate the maximum height to which m1 rises after the collision.

Kinetic energy and momentum are both conserved in the collision. The two equations allow you to solve for the two velocities after collision. Assume motion of both masses is along one axis only (forward or backward), since the collision is headon.
I will leave that exercise for you to complete. Since no figure was provided, I may end up solving the wrong situation.
If m1 is free to move upwards after collision, either up a frictionless ramp or on a pendulum string, its kinetic energy after collision will be converted to potential energy. 
mmk