Rotating Wheel - Torque and Moment of Inertia

  1. 1. The problem statement, all variables and given/known data

    A wheel free to rotate about its axis that is not frictionless is initially at rest. A constant external torque of 50N_m is applied to the wheel for 20s, giving the wheel an angular velocity of 600rev/min. The external torque is the removed and the wheel comes to rest 120s later. Find the moment of inertia of the wheel.


    2. Relevant equations

    τ=Iα
    α= ω/t


    3. The attempt at a solution

    ω=62.83rad/s
    α_1=62.83/20=3.14rad per s^2
    α_2=(-62.83)/120=-0.52rad per s^2
    50- τ_f=Iα_1
    τ_f=I(α_2)
    50=I(α_1+ α_2 )
    I=50/(3.14-0.52)
    I=19.1

    The answer should be around 27 but whatever I did I could not get that.

    Thanks
     
  2. jcsd
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