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Homework Help: Rotational Motion - Turn table

  1. Dec 13, 2011 #1
    1. The problem statement, all variables and given/known data
    4. (9) On an old style record turntable a small rubber wheel is used to drive the larger platter. They are mounted so that their circular edges touch and do not slip while in motion. The small wheel has a radius of 2.0 cm and accelerates at the rate of 3.5 rad/s2 while it is in contact with the pottery wheel of radius 28.0 cm.
    Find: a) the angular acceleration of the pottery wheel
    b) the time it takes the turntable platter to reach 33 1/3 rpm

    2. Relevant equations
    3. The attempt at a solution

    I honestly have no clue where to even begin. I have no clue how to set this up.
  2. jcsd
  3. Dec 13, 2011 #2
    The roll without slipping is all you really needed. It means the larger wheel spins as fast as the smaller wheel (as if they didn't, one would be slipping past the other).

    This means their ANGULAR accelerations are both the same. The angular acceleration is just the change in their angular velocities (per unit time of course). That should answer the first part for you.

    The second part is simple, since the acceleration is constant, the angular velocity will just be a a linear function of time.
    ω=a*t (where a is the angular acceleration). All you have to do now is change the units (through dimensional analysis or whatever you like to call it).
  4. Dec 13, 2011 #3
    Thankyou very much. I actually found an example in my book very similar to this one (My teacher is very bad at changing questions -_-) and was able to figure it out. Your explanation was very helpful though thankyou.
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