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## Homework Statement

A 32.0 kg wheel, essentially a thin hoop with r=1.20 m is rotating at 280 rev/min. It must be brought to stop in 15.0 s. How much work must be done to stop it?

## Homework Equations

/## The Attempt at a Solution

I=mr^2=46.08 kg*m^2

W=(1/2)I[tex]\omega[/tex]f^2 - (1/2)I[tex]\omega[/tex]i^2

W=[tex]\tau[/tex]([tex]\Delta[/tex][tex]\theta[/tex])

[tex]\tau[/tex]=I[tex]\alpha[/tex]

Rev in 15 sec = 70 rev => 140[tex]\Pi[/tex] radians in 15 sec.

I'm not sure which equation(s) to use. I've tried plugging numbers into all of them and getting stuck or wrong answers. Thanks!