- #1

stunner5000pt

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A heavy circular disc with radius R with mass M is fastened to a light string rod. The mass of the rod is negligible compared to the mass of the disc. The system can oscillate as a physical pendulum aout a fixed horizontal axis. The length of the rod is L.

force of gravity is [itex] mg sin \theta [/itex]

the Inertia of the disc is [itex] \frac{1}{4} MR^2 [/itex]

the inertia due to the fact that the disc is fastened to the string L is

[tex] I = \frac{1}{4} MR^2 + M (R+L)^2 [/tex]

the force due to gracvity on the CM of the disc is Mg sin theta

not quite sure how to turn that into a torque, however...

**Determine the period of small oscillations when the disc is fastened to the rod as shown, ie. when the disc swins in teh plane of the paper**force of gravity is [itex] mg sin \theta [/itex]

the Inertia of the disc is [itex] \frac{1}{4} MR^2 [/itex]

the inertia due to the fact that the disc is fastened to the string L is

[tex] I = \frac{1}{4} MR^2 + M (R+L)^2 [/tex]

the force due to gracvity on the CM of the disc is Mg sin theta

not quite sure how to turn that into a torque, however...