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Homework Help: Effect of moment of inertia on rolling distance

  1. Aug 6, 2012 #1
    Hi everyone, good day. this might be a simple question, but I need someone to check my answer.
    A disk and a hoop, of same mass and same diameter, is first giving a torque (same amount of torque for both) then the torque is removed (the torque is acting on them for the exact same period of time), causing them to roll freely without slip. The question is, which one will roll further?
    My answer to the question will be, both will roll the same distance. However, the disk will arrive at the end point first while the hoop will arrive at the end point later. Other than that, the disk will achieve higher maximum linear velocity in the process.
    Is my answer correct? This is because they are being given same amount of energy. thus the distance they can roll should be the same.
    Other than that, due to the different in mass moment of inertia, the rotational kinetic energy to translational kinetic energy ratio for disk and hoop is different. I am actually curious on what does this ratio implies? Higher ratio means more energy given is being converted to rotational KE, so? what does higher rotational KE implies? It got to be have effect on something, like the traveling time, the distance traveled, something like that. Can anyone relates these to me? Thank you very much for your time!
  2. jcsd
  3. Aug 9, 2012 #2
    Hi everyone, First of all, I am very sorry that I misplaced the post.
    Next, I noticed that the question is viewed by 135 people, but no replies. Am I not putting enough effort in solving my question? But i think i have first answered my question right?
    I am new here, so please tell me if i overlooked any rules.
    I really wish to know the answer to the questions.
    Thank you!
  4. Aug 9, 2012 #3
    If the only force acting on the rolling objects is friction with the surface they roll upon, then I think your answer is correct. However, if you take drag into consideration, things may be different.
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