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: Two radii pulley lifting a pack

  1. Mar 3, 2012 #1
    1. The problem statement, all variables and given/known data

    You are pulling on a rope attached to the outer radius of a pulley with a moment of inertia I=676 kgm2 as shown. The tension in the rope that you are pulling is 477.9 N. A pack of mass 30.8 kg is attached to the pulley's inner radius as shown. If the inner radius of the pulley is 0.56 m and the outer radius is 0.8 m, what is the magnitude of the linear acceleration of the pack?

    2. Relevant equations


    3. The attempt at a solution

    I found the tension due to the mass of the pack on the pulley.
    p=pack, at=linear acceleration of pack

    I then summed the torques, and inserted the tension due to the pack on the pulley

    solved for at=[R(Tyr)-r(mp*g)]/[(I/R)-(r*mp)]

    my final at=24.233 m/s/s which is not right
  2. jcsd
  3. Mar 3, 2012 #2


    User Avatar

    Staff: Mentor

    You might want to check your expression for Tps. Make sure that the implied forces result in an acceleration in the desired direction for the pack.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook