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Rotational Inertia


h20h

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HI I have a question hopefully someone can help me out with....the question on our homework asks: A dancer is spinning and she needs to increase her rotational inertia...I would think she would need to bring her arms in closer to one another and her legs as well? But the answer posted by our professor was to extend her arms and leg outwards?

 

I am confused a bit? Wouldn't doing that slow down her rotational interia..or is intertia a force opposing the spin so if she does that her spin would slow down but the force (intertia) would increase?

 

THanks and any help is always helpful!

 

THanks

H20h

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Inertia is the ability of a body to resist a change in it's state of motion, and not a measure of it's speed.

 

When the dancer slows down, she slows down because the moment of inertia had increased. That is clear by:

 

[math]L = \omega I[/math]

Where L is the angular momentum.

 

The moment of inerta 'I' increases, and since L remains the same, [math]\omega[/math](the spin speed) must reduce.

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