I've been busy finishing my online physics homework, and I cannot get this problem for the life of me (which is annoying because I just finished the relativity and lorentz transformation assignments). If you are good at physics and think you know how to do it, please post your line of thoughts on the matter. I've tried obvious variations of the kinematic equations of oscillation that I can think of, but no dice.(adsbygoogle = window.adsbygoogle || []).push({});

The question is below:

A wheel of mass M = 4.5 kg and radius R = 0.90 m is free to rotate about its fixed axle. A spring, with spring constant k = 270 N/m, is attached to one of its spokes, a distance r = 0.33 m from the axle, as shown in the figure. What is the angular frequency of small oscillations of this system (in rad/s)?

http://img225.imageshack.us/img225/1908/prob211yw.gif [Broken]

I was told to think of the disc as a torsional oscillator, but I had no luck doing that. If this is a pend problem I assumed (incorrectly) the axis cannot actually be the axle. It would seem to me there would only be two torques... the rotational inertia of the wheel (MR^2) and the spring. How would I calculate the torques cause by the spring though?

I thought I was to use the formula T = 2 pi * sqrt ( I / Mgd) but that obviously does not work in this case, since the wheel doesnt spin from gravity. I cannot figure out how to determine K the torque constant from the spring and substitute Mgd for K. I know angular freq = 2 pi / (T) but none the less, I only have one attempt to get this right, and I know that the way I was doing it was wrong ("practice" inputs).

Any help?

Thanks,

---Nate

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# Homework Help: Angular Freq. of small oscillations on a wheel/spring.

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