1. Not finding help here? Sign up for a free 30min 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!

Wheel and angular velocity

  1. Apr 12, 2005 #1
    Consider a bicycle wheel that initially is not rotating. A block of mass m is attached to the wheel and is allowed to fall a distance h. Assume that the wheel has a moment of inertia I about its rotation axis.

    Consider the case that the string tied to the block is attached to the outside of the wheel, at a radius r_A. Find omega_A, the angular speed of the wheel after the block has fallen a distance h, for this case.
    Express omega_A in terms of m, g, h, r_A, and I.

    Now consider the case that the string tied to the block is wrapped around a smaller inside axle of the wheel of radius r_B View Figure . Find omega_B, the angular speed of the wheel after the block has fallen a distance h, for this case.
    Express omega_B in terms of m, g, h, r_B, and I.

    Someone told me that I have incorporate torque into it. I initially thought that you needed to use the conservation of energy, etc. Any help would be great.
     

    Attached Files:

  2. jcsd
  3. Apr 12, 2005 #2
    You are correct. It is not necessary to consider torque in this problem. You need to use conservation of mechanical energy. The gravitational potential energy of the elevated mass is released as it falls and converted into the linear and rotational kinetic energies of the mass and the wheel, respectively.
     
  4. Apr 12, 2005 #3
    Ok...I got the answer. Thanks.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?