Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Rotational power

  1. Oct 18, 2006 #1
    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. jcsd
  3. Oct 18, 2006 #2


    User Avatar

    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?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook