Reaction force between a Sphere and particle

[nokia8650]

http://img13.imageshack.us/img13/9112/70948888.th.jpg [Broken]

I do not understand how circular motion can be occurring a point B - surely at B, the reaction force occurs in a direction away from O. Therefore, there is no resultant force that can be acting towards O, since the weight is perpendicular to OB.

Can someone please explain this.

Thanks

 

[Dweirdo]

http://img13.imageshack.us/img13/9112/70948888.th.jpg [Broken]

I do not understand how circular motion can be occurring a point B - surely at B, the reaction force occurs in a direction away from O. Therefore, there is no resultant force that can be acting towards O, since the weight is perpendicular to OB.

Can someone please explain this.

Thanks

Well I'm interested in this problem as well.
What I thought so far:
If we had a hoop rotating and the particle at point A-we couldn't pass point B from the exact reason You stated above.
But this time it has initial velocity, so in point B it has velocity, so there is fictitious centrifugal force,That's what i think...
well good luck..

 

[Doc Al]

I do not understand how circular motion can be occurring a point B - surely at B, the reaction force occurs in a direction away from O. Therefore, there is no resultant force that can be acting towards O, since the weight is perpendicular to OB.

Realize that the particle is riding on the inside of the sphere, just like a car on the inside of a rollercoaster loop. The surface is curved, not flat, thus the surface must press in on the particle (towards O) exerting a centripetal force on the particle.