- #1
harp AP 2010
- 30
- 0
Homework Statement
If an acrobat isn't touching the ground how can he changes his rotation speed?
Changing Rotation Speed of an Acrobat Not on the Ground
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Homework Help Overview
The discussion centers around the mechanics of an acrobat changing his rotation speed while not in contact with the ground. The subject area involves concepts of angular momentum and moment of inertia.
Discussion Character
- Exploratory, Conceptual clarification, Mathematical reasoning
Approaches and Questions Raised
- Participants explore how the acrobat can alter his rotation speed without external contact, questioning the role of body position and movement in affecting moment of inertia.
Discussion Status
Some participants have suggested that changing the position of limbs can influence the moment of inertia and thus the rotation speed. There is acknowledgment of the relationship between angular momentum and rotation speed, with considerations of how the acrobat's orientation affects these factors.
Contextual Notes
Participants are discussing the implications of the conservation of angular momentum and the conditions under which the acrobat is rotating, including whether he is aligned with a principal axis.
If an acrobat isn't touching the ground how can he changes his rotation speed?
- #2
tiny-tim
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hi harp AP 2010! 
well, what can he change without touching anything external?
well, what can he change without touching anything external?
- #3
harp AP 2010
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hi tiny-tim ;)
he can move his arms and legs, causing a change in his MoI and therefore his rotation speed?
he can move his arms and legs, causing a change in his MoI and therefore his rotation speed?
- #4
tiny-tim
Science Advisor
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hi harp AP 2010!
exactly!
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
exactly!
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
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