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Homework Help: Am I doing this right? - rotational motion

  1. Jan 12, 2006 #1
    Hint: Consider the wheel's energy.
    Consider a wheel of radius 1.23 m, mass
    7.7 kg and moment of inertia I =1/2 MR^2
    (it's a solid disk). The wheel rolls without
    slipping in a straight line in an uphill direction 30 degrees above the horizontal. The wheel starts at angular speed 16.1 rad/s but the ro-
    tation slows down as the wheel rolls uphill,
    and eventually the wheel comes to a stop and
    rolls back downhill.
    The acceleration of gravity is 9.8 m/s^2
    How far does the wheel roll in the uphill
    direction before it stops? Answer in units of

    This is what I plan to do:

    1. Use:

    1/2 Iw^2 +1/2 mv^2 = mgh

    by substituting Rw for v and solving for h.

    2. "h" would equal the "y" component so I would then go on to use trig. to find the hypontenuse.

    Would that work?
  2. jcsd
  3. Jan 12, 2006 #2
    yes, it is correct
  4. Jan 12, 2006 #3
    Thanks for the confirmation. I don't think I'm good at canceling variables out as I got the wrong answer the first time (tried to cancel out the masses). But the second time around I just plugged in everything and it came out to a different and correct answer. :)
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