Moment of Inertia and kinetic energy question

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SUMMARY

The discussion focuses on calculating the moment of inertia required for a flywheel in a gasoline engine, which must release 550 Joules of kinetic energy as its angular speed decreases from 720 rad/s to 400 rad/s. The correct approach involves using the equation for kinetic energy, K = (1/2)Iw^2, and recognizing that the change in kinetic energy is ΔK = K_final - K_initial. The correct calculation leads to the conclusion that the moment of inertia, I, must be determined using the initial and final angular velocities, not just the change in angular velocity.

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kpengin
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Homework Statement


The flywheel of a gasoline engine is required to give up 550 of kinetic energy while its angular speed decreases from 720 to 400 .
What moment of inertia is required?


Homework Equations


K=(1/2)Iw^2


The Attempt at a Solution


K=550J
I'm not sure how to get the w value since the velocity is changing.
I tried:
550=(1/2)I(320)^2
then solving for I
I=0.0107
but this is not correct.
 
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kpengin said:
I tried:
550=(1/2)I(320)^2
The right hand side is incorrect. You want Δ((1/2)Iw^2), not (1/2)I(Δw)^2.
 

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