When the small m slides from the lower end to the upper end, the conservation of mechanical energy is 2 = mg2r+ 1/2mv, and the velocity after collision can be obtained from 2 = v.
When two objects collide, momentum is conserved: when Mv=Mv*+mv, the velocity of large M sliding down the low end can be obtained, and v=
The law of conservation of mechanical energy in the process of large m sliding: Mgh= 1/2Mv2, and then h= can be obtained.
I can't get a square because I can't mark it. I added 2 at the end. I'll see for myself. I should know the train of thought. I hope to learn and make progress.