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Velocity at P

  1. Jan 8, 2004 #1
    Hi. I think this is my 1st post here but I browse a lot on the forum :smile:
    I was trying to know the velocity at a point on a rigid Body (in 2D) and i found this equation on a paper:
    [​IMG]
    where:
    Vap = velocity at point P (body A)
    Va1 = Linear Velocity of the Rigid Body CM (m/s)
    w1 = Angular Velocity of the Rigid Body (rad/s)
    rap with a invers "T" = the perpendicular distance vector from the CM to point p.

    Im working on 2 dimension here so angular velocity is just a scalar

    The question i have is the unreal result that this equation gives to me, for exemple:
    Va1(0, -5)
    w1=1.5;
    rap(-5,-20) -> now we take the prependicular vector (90º to the left)
    rapT(20, -5);
    and if im not mistak making the calculations
    Vap = (0,-5) + ( 1.5*20 + 1.5*(-5))
    Vap = (0,-5) + ( 30+(-7.5))
    Vap = (0,-5) + 22.5 = (22.5, 17.5);
    Vap=(22.5, 17.5)

    I think this value is too high, are my calculations wrongs ?
    HELP ME
     
  2. jcsd
  3. Jan 9, 2004 #2

    HallsofIvy

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    Staff Emeritus
    Science Advisor

    Why is that "unreal"? This object is not moving very fast in translation but it is spinning like heck and it's pretty darn big.
     
  4. Jan 9, 2004 #3
    maybe ur right

    well now that i look better the angular velocity is in rad's!!!!
    lool forgot that
    Thanks.
     
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