- #1
xxxyyy
- 14
- 2
Hi,
I'm missing something really stupid here...
The problem is the usual one with a block sliding down (or moving up, it should be the same) a frictionless inclined plane,which itself is free to move on a orizontal frictionless surface.
These problems are usually solved stating that only gravitation (conservative) does work.
Don't the reactions do work too?
The reaction on the block is orthogonal to the plane, but not orthogonal to the path of the moving block, the inclined plane is moving, so it does work (negative)
The reaction on the inclined plane has a component in the direction of the movement of the plane itself, so it does positive work.
They should cancel, but how to show it? Energy conservation because there's no friction? But if so they should have started from energy conservation, I guess?
Thank you!
I'm missing something really stupid here...
The problem is the usual one with a block sliding down (or moving up, it should be the same) a frictionless inclined plane,which itself is free to move on a orizontal frictionless surface.
These problems are usually solved stating that only gravitation (conservative) does work.
Don't the reactions do work too?
The reaction on the block is orthogonal to the plane, but not orthogonal to the path of the moving block, the inclined plane is moving, so it does work (negative)
The reaction on the inclined plane has a component in the direction of the movement of the plane itself, so it does positive work.
They should cancel, but how to show it? Energy conservation because there's no friction? But if so they should have started from energy conservation, I guess?
Thank you!