# Homework Help: Angular speed question

1. Nov 6, 2009

### Dr_bug

1. The problem statement, all variables and given/known data

A 320 N sphere 0.20 m in radius rolls, without slipping, 6.0 m down a ramp that is inclined at 25° with the horizontal. What is the angular speed of the sphere at the bottom of the hill if it starts from rest?

2. Relevant equations
I sphere= (2/5)mr^2
atan=rα
v=rω

3. The attempt at a solution
I tried first to use F∆x=(1/2)*[(2/5)mr^2]ωf^2-0(zero because it starts from rest) but then i realize i don't have a mass and now i don't really know what to do. any helpful hints or suggestions would be appreicated

2. Nov 6, 2009

### rock.freak667

At the top, it only has potential energy mgh. At the bottom, the energy is entirely kinetic. Do you see why you don't need the mass?

3. Nov 6, 2009

### Dr_bug

so then can i just solve the eqn i was using and just ignore m?

4. Nov 6, 2009

### rock.freak667

No your equation is correct. Just what is the force F in $F\Delta x$?