Suppose I have a rotating sphere with a circumference of 13000 km, on this sphere are items whose weight is evenly distributed. Now I move a weight of 1.5 billion kilos towards the axis, what will happen to this sphere?
Answer
In principle, the whole thing then runs faster.
This is the law of conservation of angular momentum (sometimes called torque): the sum over all parts of mass times distance-from-axis-square times rotational speed remains constant.
The exact terms for this may be too long to discuss here. A case where it works this way anyway is when you are also standing on the sphere and therefore step on the sphere (i.e. push) to move the weight.
This is the same effect you can see in spinning skaters: when they keep their arms close to the axle, they spin faster than when they extend their arms.
Answered by
prof.dr.ir. Alan Sarlette
control engineering, automation, robotics, dynamical systems, applied mathematics, quantum physics
http://www.ugent.be
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