Changing Rotation Speed of an Acrobat Not on the Ground

AI Thread Summary
An acrobat can change his rotation speed while in the air by adjusting his body position, specifically by moving his arms and legs. This movement alters his moment of inertia (MoI), which affects his angular velocity according to the conservation of angular momentum. If he rotates along a principal axis, his rotation direction remains constant while his speed changes. However, if he is not rotating along a principal axis, both his speed and direction may change. Understanding these principles is crucial for analyzing rotational dynamics in acrobatics.
harp AP 2010
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Homework Statement


If an acrobat isn't touching the ground how can he changes his rotation speed?


Homework Equations





The Attempt at a Solution

 
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hi harp AP 2010! :wink:

well, what can he change without touching anything external? :smile:
 
hi tiny-tim ;)
he can move his arms and legs, causing a change in his MoI and therefore his rotation speed?
 
hi harp AP 2010! :wink:

exactly! :smile:

if he moves his arms or legs in or out, or even if he bends at the waist, his https://www.physicsforums.com/library.php?do=view_item&itemid=31" will stay the same …

if he was originally rotating along a principal axis (so his angular velocity is in the same direction as his angular momentum), his rotation direction will stay the same, but the speed will change;

if he wasn't originally rotating along a principal axis, his rotation direction will precess also :wink:
 
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