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Old Oct 14th 2014, 06:32 PM   #1
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Ice skater and solid cylinder questions

(a) An ice skater with an initial moment of inertia of 1.34 kgm2 with arms outstretched horizontally is initially spinning at 9.10 revs/s. She draws her arms vertically in by her side reducing her moment of inertia to 1.25 kgm2. What is her new angular velocity?
(b) A solid cylinder with a diameter of 36.8 cm and mass 13.2 kg is rolling on a horizontal surface with a linear velocity of 1.76 m/s.
Calculate the angular momentum of the cylinder.

I got 61.3 rad/s for the final angular velocity for the skater

and for b I got Moment of Inertia I= 0.22 and angular momentum L=2.1

Can someone please check if I did these correctly ?

It would be greatly appreciated !
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Old Oct 15th 2014, 07:58 AM   #2
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Very good - I get the same results. Just don't forget to include units.
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Old Oct 15th 2014, 01:57 PM   #3
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Thanks so much !
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Old Oct 15th 2014, 08:12 PM   #4
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angle of wheel turn

OK this one has me stumped as not sure which way to go.

A wheel was rotating at 11.5 rad/s when a torque was applied for 12.7 secs. The angular velocity increased to 47.0 rad/s.


What angle did the wheel turn through in that time?



I tried to use one of the kinematics formulas after working out he acceleration to get the angle but I don't think it is working.... help ? I got 370.84 ??
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