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Mechanical Engineering Thursday Seminar Series, 530.803
Thursday, November 19, 2009
3:00 PM, 210 Hodson Hall
" Rotation with Zero Angular Momentum: Demonstrations of the Falling Cat Phenomenon Go Sour"
Presented by Professor Andy Ruina
Cornell University
It is well known that a system with zero angular momentum can, by appropriate deformations, rotate while preserving the condition of zero angular momentum. This effect explains how a cat that is dropped while upside down can turn over and of how certain gymnastic maneuvers are performed. These rotations are taken as a demonstration of the "non-integrability" of a "non-holonomic" constraint. There is a simple demonstration of this rotation-with zero-angular- momentum effect with a rotating platform. But the demonstration often doesn't work because most floors are not perfectly flat. I found a simple better demonstration experiment. Unfortunately, the experiment came out all wrong for different reasons. But I figured out why and did a second demonstration experiment. And that came out wrong exactly in the opposite way.
The talk presents the four puzzles: a) how can you turn while having zero angular momentum? b) Why does a rotating platform demonstration often not work? c) Why does a simple demonstration not work? d) Why does almost exactly the same demonstration not work in the opposite way?
The talk starts with various personal stories about non-holonomic constraints and their relation to locomotion, like bikes skates and walking, and then gets into the 4 rotation puzzles.
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Graduate Seminar in Fluid Mechanics, 530.807
Friday, November 20, 2009
3:00pm, 120 Latrobe Hall
“TBA”
Presented by
Yuan Lu
TBA
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Friday Solids Seminar
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