1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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