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: Stopping a rotating disk with an axe

  1. Mar 16, 2005 #1
    My problem:
    A grindstone in the shape of a solid disk with diameter=0.480m and a mass of m=50.0kg is rotating at omega = 820rev/min. You press an ax against the rim with a normal force of F=190N View Figure , and the grindstone comes to rest in 8.00s.

    I need to find the coefficient of friction between the ax and the grindstone.

    well the stuff i have some far is that the moment of Inertia is 1/2MR^2. That is really all that I have I just need a hint or something on how to proceed...if someone could help me out.
    Last edited: Mar 16, 2005
  2. jcsd
  3. Mar 17, 2005 #2


    User Avatar
    Science Advisor
    Homework Helper

    The axe exerts a constant torque [itex]\tau = I\alpha[/itex] on the disk, combine this with the 'equation of motion' for the angular velocity: [itex]\omega(t)=\omega_0+\alpha t[/itex].
  4. Mar 17, 2005 #3
    Galileo, thank you. That really helped me figure the problem out.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook