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Homework Help: A Crate on an Incline

  1. Oct 26, 2009 #1
    1. The problem statement, all variables and given/known data

    A wheel of radius R = 30.0 cm is mounted on a frictionless horizontal axis. A massless cord is wrapped around the wheel and attached to a 4.75-kg crate that slides on a frictionless surface inclined at an angle of 25.0° with the horizontal. The crate accelerates down the incline at 2.4 m/s2.

    (a) What is the tension in the cord?

    (b) What is the rotational inertia of the wheel about its axis of rotation?

    2. Relevant equations

    I = MR^2

    I = Inertia
    M = Mass
    R = Radius

    3. The attempt at a solution

    I thought I could solve for part (b) using the above formula but I am not getting the correct answer. And I am not even sure how to start on part (a). Any help will be appreciated.
    Last edited by a moderator: Apr 24, 2017
  2. jcsd
  3. Oct 27, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    You're not given the mass, nor can you assume that the wheel is a uniform disk. So that won't work. First solve part (a), then use it to solve (b).
    What forces act on the crate? Apply Newton's 2nd law.
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