Re: [Phys-L] spinning skater

["LaMontagne, Bob" <RLAMONT@providence.edu>]

Since KE=L^2/(2 I)  with L being angular momentum and I being the moment of inertia

Then the work done by the skater is

Work=L^2 / (2 I) - L^2 / (2 Io)      with Io being original I before pulling arms in.

Bob at PC
________________________________________
From: Phys-l [phys-l-bounces@phys-l.org] on behalf of Bernard Cleyet [bernardcleyet@redshift.com]
Sent: Sunday, May 12, 2013 9:05 PM
To: Phys-L@Phys-L.org; curtis osterhoudt
Subject: Re: [Phys-L] spinning skater

On 2013, May 12, , at 14:11, curtis osterhoudt <flutzpah@yahoo.com> wrote:

> Many students draw parallels with the figure skater, not having realized that the figure-skater's arms have to pull at *an angle* to a radial vector in order to be drawn in, and therefore exert a torque on the skater's body, too.

I presume work is "done" doing this.  What is the connection between conservation of L and E in the skater prob.?

bc last "dealt" w/ mechanics in '63 (Goldstein).


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