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Homework Help: Gravity probe b gyroscope

  1. Mar 15, 2004 #1
    In GPB's experimental conditions, a negligible amount of precession takes place.

    So in terms of rotational inertia, why does the spin axis of a gyroscopes remain pointing in the same direction?

    Also, why would changes in space-time cause the axis to change?

  2. jcsd
  3. Mar 16, 2004 #2
    Actually i understand the second part, just not the rotational inertia bit
  4. Mar 16, 2004 #3
    Because of the conservation of angular momentum. In absence of a torque the angular momentum of the gyroscope is conserved. This is basically the rotational analog of Newtons second law for conservation of 'normal momentum' in absence of a force.

    The angular momentum, which is a vector, points in the direction of the spin axis, because it is the crossproduct of the radius and momentum of the gyroscope. In absence of a torque the gyroscope will spin with a constant speed AND direction. So the spin axis of the gyroscope will remain pointing in the same direction.
    Last edited: Mar 16, 2004
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