Calculating Rotational Kinetic Energy of a Baton

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Homework Help Overview

The discussion revolves around calculating the rotational kinetic energy of a baton being twirled by a drum major. The problem involves concepts from rotational dynamics, specifically focusing on the moment of inertia and angular velocity.

Discussion Character

  • Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to calculate the rotational kinetic energy using the formula KE_rot = 0.5 I w^2, but encounters an issue with their moment of inertia calculation. Some participants question the accuracy of the moment of inertia and suggest verifying the formula used.

Discussion Status

Participants are actively engaging in clarifying the calculations related to the moment of inertia and its impact on the final result. There is a suggestion that the original poster's revised calculation may be correct, but confirmation is still sought.

Contextual Notes

The original poster expresses uncertainty about their calculations and seeks validation before submitting their answer. There is an indication of potential confusion regarding the application of the moment of inertia formula.

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Homework Statement


A drum major twirls a 94-cm-long, 500 g baton about its center of mass at 150 rpm. What is the baton's rotational kinetic energy?

Homework Equations



KE_rot = 0.5 I w^2

The Attempt at a Solution


w = (150rpm*2pi)/60 = 15.708rad/s

I = (1/12)*0.5kg * 0.94m = 0.039167kg*m^2

KE_rot = 0.5 I w^2

KE_rot = 0.5(0.039167)(15.708rad/s)^2
= 4.8J

says wrong answer.
Cant figure out what I am doing wrong
thanks for any help
 
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Take a look at the moment of inertia: you do kg times m and you obtain kg m^2.
 
thanks..ok forgot to square so I = (1/12)MR^2
I = (1/12) 0.5kg ((0.94m)^2) = 0.03682kg*m^2

so KE_rot = 0.5(0.03682)(15.708rad/s)^2 = 4.5J

(i just want to confirm correct before I submit answer again)
thanks for the help
 
I think it is correct.
 

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