Rotation problem: which would stop first?

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The discussion revolves around a physics problem regarding two fans of different sizes and which one would stop first after being turned off simultaneously. The original poster, a 9th grader, is unsure how to approach the problem and believes the smaller fan will stop first. Participants suggest considering factors like angular velocity, torque, and energy loss related to the fans' sizes. They encourage the poster to think about the relationship between radius and energy in the context of the problem. Understanding these principles is essential for solving the question effectively.
Misako
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Hey! I'm new here in PF and is wanting to solve this teeny bitsy problem about rotation. I'm at 9th grade and is a newbie at physics. :p

Homework Statement



Two razor fans, one larger and one smaller, were turned on at the same time and turned off at the same time.

Question: which fan would stop first? the larger one or the smaller one?


Homework Equations



I'm thinking of: angular velocity = delta s/ r x delta t

The Attempt at a Solution



I need to prove the answer by using an equation. So the equation must include probably a radius(for the smaller and larger blade) and the time. Problem is, i can't seem to find that and is stumped. But for me, I really think the smaller fan would stop first.

Halp? =(
 
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Welcome to PF.

Has torque been discussed in your class?
 
Welcome to PF!

Hi Misako! Welcome to PF! :smile:

hmm … that seems rather difficult for 9th grade :redface: …

let's assume they're turning at the same angular rate …

what is the initial energy proportional to, r r2 or r3?

and what is the rate of energy loss proportional to? :smile:
 

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