Conservation of Angular Momentum in Skater's Spin Rate Change

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Homework Help Overview

The discussion revolves around the conservation of angular momentum in the context of a figure skater changing her spin rate by drawing her arms in. The original poster presents a scenario where the skater's rotational inertia decreases, prompting questions about the resulting change in her rate of rotation.

Discussion Character

  • Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to apply a formula to find the new rate of rotation but questions the correctness of their approach. Other participants suggest using the principle of conservation of angular momentum and encourage writing out the relevant equations.

Discussion Status

Participants are exploring the relationship between initial and final angular momentum. Some guidance has been offered regarding the need to express angular momentum mathematically, but there is no explicit consensus on the correct approach or solution yet.

Contextual Notes

The original poster expresses uncertainty about the equations to use and indicates that their initial calculation does not match expected results. There is an implication of homework constraints, as the poster seeks assistance without revealing complete methods.

Devin Longo
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Homework Statement



A figure skater is spinning at a rate of 2 rev/s with her arms outstretched. She then draws her arms into her chest, reducing her rotational inertia to 61% of its original value. What is her new rate of rotation?



Homework Equations



?



The Attempt at a Solution



w/2 = 1/sqrt(0.61)
w = 2.56 rev/s

This isn't correct according to the website, can someobody help me with a better equation and how to solve this one?

Thanks!
 
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angular momentum before = angular momentum after
 
I still don't really understand
 
Angular momentum is conserved; it stays the same unless there is an external torque. So
angular momentum before = angular momentum after

You need to write the formula for angular momentum on both sides. Fill in the quantities you know and solve for the one you want to find.
 

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