Solving Angular Velocity Homework: Mass, Friction & Work

AI Thread Summary
The discussion revolves around a physics homework problem involving a puck in uniform circular motion on a frictionless table. The student is tasked with calculating the work done when the string is pulled down by 0.5 meters while maintaining a fixed radius of 0.8 meters. Key equations mentioned include the conservation of kinetic energy and the moment of inertia of the puck. The student struggles to determine the final angular velocity after the string is pulled. Suggestions include using the conservation of angular momentum to solve for the unknowns.
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Homework Statement


a small puck of mass .5kg is executing Uniform constant motion on a friction free horizontal table. The angular frequency of the puck is 10 sec-1 (counter clockwise) and the radius of the circular motion is .8m. the radius stays fixed as the student holds the string in place. he now pulls the string down .5 m and holds it again in place. what work did he do?


Homework Equations



KE(original)+ W = KE (final)
inertia of hockey puck on string = mr2
w = angular velocity
I = inertia

The Attempt at a Solution


KE(original)+ W = KE (final)
.5(I)w2 +W = KE final
.5 (.5)(.8)2(102) + W = KE final

now i have a problem solving for kinetic energy final...
KE final = .5(.5)(.5)2(102)(w2)
I can't figure out what w (angular velocity) is...
please help!
 
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