Momentum conserved on inclined ramps?

[aeromat]

Homework Statement

Is momentum conserved if an object is rolling down an inclined plane?

This is just a question that I was thinking over in class the other day, because the most of the coursework done was involved with collisions between two objects. Wouldn't this also be considered the case for this question since as the object is rolling down, it is constantly colliding with the ramp..

 

[ideasrule]

The momentum of what? The momentum of a system (not of individual objects) is conserved if and only if the force acting on the system is 0. The force acting on a rolling ball is not 0, so its momentum is not conserved. However, if you consider the system consisting of the ball, the ramp, and the Earth, that system's momentum is conserved.

 

[aeromat]

By force acting on the system, you mean the "net force" must equal 0? And yes, I was talking about the second situation that you stated.

 

[ideasrule]

Yes, I mean net force.