Rotational power

1. Oct 18, 2006

bearhug

A 32.0 kg wheel, essentially a thin hoop with radius 1.20 m is rotating at 280 rev/min. It must be brought to a stop in 15.0s
What ist the required average power to do this?

I know that P=τω
To find τ I used the equation τ=Fd where F=ma I figured I would find a by using the equation ωf= ωi + αt
First off is this the right approach? I'm also confused as to what d is. My book doesn't really explain it that well, would d be = 1.20m?

Thanks for any help

2. Oct 18, 2006

Staff: Mentor

Another way to approach this problem is to calculate the initial rotational energy, then the average power is just delta-E / delta-t

What is the rotational E in terms of the moment of inertia and rotational velocity? How do you calculate the moment of inertia for the wheel as described?