- #1
jaumzaum
- 434
- 33
Consider a slope with mass, that can move in the horizontal plane without friction. A ball is dropped and hits the slope with restitution coefficient e. How to calculate the final velocities?
How can I solve something like this? Note that it's not a simple 2D collision, it has a restriction that the slope can only move in the horizontal plane. There are actually 2 collisions happening, the collision of the ball with the slope (partially inelastic) and the collision of the slope with the Earth (that is completely inelastic). What is the meaning of the restitution coefficient in this problem? Will it be the restitution coefficient for the first collision or for the overall collision? I know the answer could be "well, it could be for both, you need to specify", but practically, do I really need to specify this? Isn't anything implied?
I have another problem when I try to think about the energy dissipated in the problem. The first collision will drain energy from the ball and convert in another type of non-translacional kinetic energy. If the second collision happened after the first (the ball hits the slope and then the slope hits the ground), the second collision would drain energy only from the slope. That way we could say there would be 2 different restitution coefficients. But both things are occurring at the same time, so I don't know if this "second collision" will drain energy only from the slope anymore, it could drain energy from the ball, and the final velocity of the ball when both collisions happens simultaneously could actually be different from those calculated if the collisions happened one another.
How can I solve something like this? Note that it's not a simple 2D collision, it has a restriction that the slope can only move in the horizontal plane. There are actually 2 collisions happening, the collision of the ball with the slope (partially inelastic) and the collision of the slope with the Earth (that is completely inelastic). What is the meaning of the restitution coefficient in this problem? Will it be the restitution coefficient for the first collision or for the overall collision? I know the answer could be "well, it could be for both, you need to specify", but practically, do I really need to specify this? Isn't anything implied?
I have another problem when I try to think about the energy dissipated in the problem. The first collision will drain energy from the ball and convert in another type of non-translacional kinetic energy. If the second collision happened after the first (the ball hits the slope and then the slope hits the ground), the second collision would drain energy only from the slope. That way we could say there would be 2 different restitution coefficients. But both things are occurring at the same time, so I don't know if this "second collision" will drain energy only from the slope anymore, it could drain energy from the ball, and the final velocity of the ball when both collisions happens simultaneously could actually be different from those calculated if the collisions happened one another.