- #1
jcruise322
- 36
- 1
Homework Statement
A uniform solid ball of mass m and radius R rolls without slipping down a plane inclined at an angle f above the horizontal. Find the frictional force and the acceleration of the center of mass.[/B]
Homework Equations
τ=I*α
so:
fs*r=I*a
Mg-Fs=ma
Moment of inertia for sphere about center of mass: 2/5*I
Moment of inertia for rolling sphere: 7/5*I
The Attempt at a Solution
I understand how to do the problem, I am just confused about why exactly we use the center of mass moment of inertia for "I" (2/5*I) in Newtons second law Torque equation. Is it just by definition...? the moment of a rolling sphere is actually 7/5*I according to the Parallel Axis Theorem. I understood it before I learned the Parallel theorem, now I am just a tad bit confused. An input would be great, thanks! :)
*also, hopefully this is the correct format and everything, I am new to this site*
[/B]