Physics Help Forum Ice skater and solid cylinder questions

 Periodic and Circular Motion Periodic and Circular Motion Physics Help Forum

 Oct 14th 2014, 07:32 PM #1 Junior Member   Join Date: Aug 2014 Posts: 9 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 !
 Oct 15th 2014, 08:58 AM #2 Physics Team     Join Date: Jun 2010 Location: Naperville, IL USA Posts: 2,271 Very good - I get the same results. Just don't forget to include units.
 Oct 15th 2014, 02:57 PM #3 Junior Member   Join Date: Aug 2014 Posts: 9 Thanks so much !
 Oct 15th 2014, 09:12 PM #4 Junior Member   Join Date: Aug 2014 Posts: 9 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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