# Force and moment question on a sphear

1. Apr 13, 2006

### danielI

http://img457.imageshack.us/img457/7227/problem8sp.png [Broken]

If a ball is affected by a force P OR a moment M, what will this force or moment have to be in order to make the ball roll over the edge.

My initial guess is that the force $$F\cos a$$ has to equal (or be greater?) mg, where m is the mass of the ball. Now I need some help in order to figure this out. Will the force P equal the force F or will it equal $$F\sin a$$? My guess is also that the force F is pointing towards the center of the ball. This should make it easy to calculate the angle a since if we draw a triangle from the center of the circle to the edge of that "stair" we will have a height of (r-h) and the hypotenuse will be r (r equals the radius).

Also I could need an extra help with getting the same result through the moment. I know I could turn the moment into a force but then the force would be pointing down (or up, depending on the distance).

Greatly thankful for any support you could provide.

Last edited by a moderator: May 2, 2017