Calculate the frictional force if the ball is not slipping

[Punkyc7]

Homework Statement

You have a ball rolling down an inclined plane of h height and an angle theta. I have to calculate the frictional force if the ball is not slipping

Homework Equations

t= FRsin theta
I=2/5mR^2

The Attempt at a Solution

Where on the ball is the torque being measure is it the center of gravity or is it at the outer most region of the ball. The ball is solid.

 

[kjohnson]

In reality torques (moments) can be sumed about any point, but it will generally be easiest to sum torques about the center of gravity. In this case the only torque present will be that due to friction and will result in the equation of motion of (f)(r)=I(alpha) where f is force friction, r is radius, and I is moment of inertia. From this you just need to solve for alpha when no slipping is present.