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Homework Help: Angular velocity vs normal velocity

  1. Dec 10, 2009 #1
    1. The problem statement, all variables and given/known data

    Okay, imagine there is a rod floating in space, except its not moving and not rotating. you are stationary next to the rod. you decide to push the rode with your finger at a spot "x" distance away from it's centre of mass. how much of that force will turn into plain speed and how much will turn into angular velocity. because the rod wont just move, it will also start spinning.

    2. Relevant equations

    I think this is really what i want to find out, equations that will help me understand what is going on, and a way to solve this kind of thing in the future.

    3. The attempt at a solution

    I dont really have one at all. Each line of thought i have usually ends with me realising thats wrong! Anyway, this is not dreadfully urgent but i am quite curious about an answer. :)

  2. jcsd
  3. Dec 10, 2009 #2

    Doc Al

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    Staff: Mentor

    To find the translational acceleration of the center of mass, apply Newton's 2nd law for translation: F = ma. (It doesn't matter where you apply the force.)

    To find the rotational acceleration (alpha) of the object about its center of mass, apply Newton's 2nd law for rotation: Torque = I alpha. (To calculate the torque, it does matter where the force is applied.)
  4. Dec 11, 2009 #3
    Ahh yes, Thank you Doc Al. That put me on the right track :). I want to apply this in a physics engine that uses impulses to stop interpenetration. So knowing how to turn those impulses (applied to a point in a certain direction) will affect the rotational velocity is the objective.

    Many Thanks.
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