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Homework Help: Angular Momentum

  1. Apr 19, 2009 #1


    A gyroscope is turning such that in the picture the top of the wheel is coming out of the page and the bottom of the wheel is going into the page (the wheel is rotating in the sense of the curved arrow). The bar (which is attached to the center of mass of the wheel and of negligible mass) is being held up by a piece of string wrapped around its end.

    3) Which direction does the angular momentum vector of the gyroscope point in?

    A. +x
    B. -x
    C. +z

    4) The direction of rotation (precession) of the gyroscope is:

    A. counterclockwise in the plane of the page (rotating in the direction from the x-axis to the y-axis)

    B. out of the page (rotating in the direction from the x axis to the z axis)
    C. into the page (rotating in the direction from the x axis to the -z axis)

    ANSWER: 3) I believe to be A (+x) because using the right hand rule, by following the motion of the rotation, your thumb points in the positive x direction.

    4) I think the direction of precession will go into the page (C) because of how the wheel is spinning, it wants to travel to the -z axis.

    Can somebody please help check these problems, I would really appreciate it. I pasted a link to the diagram on the very top of my post. Thanks in advance.
  2. jcsd
  3. Apr 19, 2009 #2


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    3) Looks right.

    4) Looks right.
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