- #1
Tina20
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Homework Statement
A 45.8 kg figure skater is spinning on the toes of her skates at 1.18 rpm. Her arms are outstretched as far as they will go. In this orientation, the skater can be modeled as a cylindrical torso (41.3 kg, 18.6 cm average diameter, 167.0 cm tall) plus two rod-like arms (2.24 kg each, 70.1 cm long) that each rotate about an axis through the inner end of the rod. The skater then raises her arms straight above her head, where she appears to be a 45.8 kg, 18.6 cm diameter, 199.0 cm tall cylinder. What is her new rotation frequency, in radians per second?
Homework Equations
I have no idea how to go about this question.
Some potentially useful equations:
Iiwi = Ifwf
where i = initial, f = final
I = moment of interia
w = angular velocity
I for a rod about end = 1/3ML^2
I for cylinder or disk about center = 1/2MR^2
The Attempt at a Solution
Iiwi = Ifwf
(Iarm + Iarm + Ibody)wi = (Ibody)wfinal
(2Iarm + Ibody)wi = (Ibody)wfinal
(2(1/3ML^2) + 1/2MR^2)wi = (1/2MR^2)wf
So I tried the above equation, but my answer is coming out wrong :( Any help please!