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Dealing with angular momentum of rigid bodies

  1. Jun 6, 2012 #1
    I'm taking dynamics of rigid bodies, I'm having some trouble with impulse and momentum.
    Basically ,I know that angular momentum abt. a point ,is the linear momentum multilied by the moment arm .
    BUT ,I'm not feeling at all comfortable appliying it
    For example , When is H abt. a pt. p = (moment of intertia abt. p )(w) and when is it m*V*d ,and when is it Ig*w +mVg *(d) ,i'm very confused about the whole thing and when to apply what so any clarification on the subject would be very helpfull , preferably I would like the most general case stated and explained,than when to cancel out terms and why to get to more specific cases .....
    ANY clarification/comment can be helpfull
    Thanks
     
  2. jcsd
  3. Jun 6, 2012 #2
    I think your question is not being answered because it's pretty broad....I'm not even sure where to start to assist.

    I'd suggest you read a first year physics book on rotational kinematics, linear and angular relations,rotational variables, stuff like that...

    If you understand F = ma for translational motion, you can start by figuring out the rotational analogies: Torque [T} becomes the analogy of force [F] and rotational inertia becomes the analogy of mass. The lattter gets a bit tricky because the distribution of mass relative to the axis of rotation is important. And acceleration [a] becomes angular acceleration, alpha.

    So for example, instead of kinetic energy being 1/2mv2 the rotational
    analog is 1/2Iw2 where m is replaced by I and v = wr. I has different values for different shapes, even when the total mass is the same.
     
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