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Homework Help: Angular Acceleration Help Needed!

  1. Apr 25, 2004 #1
    Heres the problem. I'm trying to solve it at the moment, and I'll be posting what I have done so far. I'm very short on formulas for this so I will need help. Thanks a lot.

    1) a) Determine angular acceleration of a wheel, which has a velocity of 200 rad/min after rotating for 1.5s from start.
    b) If the wheel has a rotational inertia of 5500 kgm2(squared), what would be its radius if 5000 N of forced had been applied?
    c) If the same wheel, having reached a final velocity of 200 rad/min, were slowed down with a constant torque of 10,000 NM applied (with same radius), how long would it take to stop the wheel?
    d.) How much force was applied?
    e.) Determine the mass of the wheel. (the wheel is a solid disk)

    Again, your help would be greatly appreciated.
  2. jcsd
  3. Apr 25, 2004 #2
    Ok, heres what I'm thinking.

    a.) (200/60)rad/min = (10/3)rad/s
    Angular Acceleration = (dW/dT)
    (3.33rad/s)/(1.5s) = 2.22 rad/s^2

    b.) I = MR^2 F = Ma
    5000N = (M)(2.22rad/s^2)
    M = 2252.25 kgm/rad

    I = MR^2
    (5500kgm^2) = (2252.25kgm/rad)(R^2)
    R = 1.56 m/rad

    c.) No idea. Please Help
    d.) No idea. Please Help
    e.) No idea. Please Help
  4. Apr 25, 2004 #3
    Possibility for Part C

    Angular Displacement = (W^2-Wo^2)/(2*Angular Acceleration)
    = (11.11rad^2/s^2)/(4.44rad/s^2)
    = 2.5 rad
    Angular Displacement = (t/2)(Wo+W)
    =(2.5 rad) = (t/2)*(10/3rad/s)
    =(2.5 rad)/(3.33rad/s)
    = .75s = (t/2)
    t = 1.5 s

    Now, I think I solved that part, but I didn't end up using Torque or the Radius, so my answer could be wrong. Please reply with any comments
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