# Friction acting on a ball on an inclined plane

1. Jul 20, 2010

### Mattowander

I just have a quick question. I know that at least some amount of friction is required in order for a ball to roll down an inclined plane and not just slide. My question is about the work done by friction in this situation. Is all of this energy converted to rotational kinetic energy or is there a loss of mechanical energy? Does it depend on how much friction there is between the ball and the ramp? I would appreciate any insight that you guys could give me on this situation.

2. Jul 20, 2010

### Staff: Mentor

Since the ball rolls without sliding, there is no work done by friction. Note that the friction involved is static friction.
Even though no work is done by friction, it does cause energy to be transformed into rotational KE. In the ideal case, there would be no loss in mechanical energy. (Of course, in real life there is rolling friction, deformation, etc., which does dissipate mechanical energy.)
For any given angle, there is a certain amount of friction required. (You can calculate the needed friction using Newton's laws applied to translation and rotation.) If the surfaces are unable to provide that amount of friction, you'll get sliding.