- #1

- 120

- 26

- Homework Statement
- Two identical frictionless slides A and B each of height h and mass M are placed on a horizontal frictionless floor. A small disc C of mass m much less than M is released on the top of the slide A. Find expressions for the speeds eventually acquired by both the slides when interaction of the slides with the bead ceases. (see fig. 1)

- Relevant Equations
- Work- energy

Firstly, what I'm about to do is to find the velocity of the mass soon after it doesn't touch the slide A anymore.

using momentum conservation, I got ##0 = mv' + MV'## with ##v'## and ##V'## are the velocity for mass C and slide A respectively immediately after they lost interaction.

Now, I need one more equation. However, I doubt that energy is conserved here because the slide is free to move, and this will cause the contact force between them does Work. But, when I watch the solution video, I'm surprised to know that energy is conserved if we consider slide A.B and mass C is one system. I wonder why...