A block of mass m1= 5kg is released from point 1 which is 5 meters above the horizontal frictionless surface and slides down a frictionless track. It makes a head-on collision at point 2 with a block of mass m2= 10kg that is initially at rest. Calculate the maximum height to which m1 rises after the collision.
I don't know where to start... The problem doesn't give the distance between m1 and m2, just how far m1 is above the ground.