How Fast Must a Block Slide to Circle a Loop After Inelastic Collision?

[physicslover11]

Homework Statement

A block of mass m slides along a frictionless track with speed vm. It collides with a stationarty block of mass M. Find an expression for the minimum value of vm that will allow the second block to circle the loop the loop without falling off if the collision is perfect inelastic.

Homework Equations

Uinitial+Kinitial=Ufinal+Kfinal
U=mgh
K=1/2mv^2

The Attempt at a Solution

Since this is a frictionless track, there is no initial kinetic energy, but that is all i really can figure out i am completely lost someone please help!

 

[mfb]

It is easier to consider this problem backwards: At the top of the loop, the masses are supposed to stay in their track. Which forces act on them? How can they stay in the track, and which velocity do they need?

The masses come from the bottom of the loop. What was their velocity there?

And afterwards, consider the collision.