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tachu101
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Homework Statement
A hoop of mass 1kg and radius 2m is rotating about its center with an angular speed of 3rad/sec. A force of 10N is applied tangentially at the rim.
a. The rotational kinetic energy of the hoop is?
b. The instantaneous rate at which the kinetic energy is changing is?
Homework Equations
KE= 1/2Iw^2
The Attempt at a Solution
For the first part I can find I= MR^2 for a hoop, so I= (1)(2^2) so I=4. So KE= 1/2Iw^2 = (1/2)(4)(3^2)= 18. What do I do with the extra 10N applied (do I just add it in or does it not factor into the rotational kinetic energy?) I don't know what equation to use for the second part.