(adsbygoogle = window.adsbygoogle || []).push({}); Please Help!!!(damped pendulum)

A physical pendulum consists of an L = 70 cm long, 100 g mass, uniform wooden rod hung from a nail near one end (Fig. 14-38). The motion is damped because of friction in the pivot. The damping force is approximately proportional to d(theta)/dt. The rod is set in oscillation by displacing it 15° from its equilibrium position and releasing it. After 10 seconds, the amplitude of the oscillation has been reduced to 4° . Assume that the angular displacement can be written as

theta= A*e^(-alpha*t)*cos(w'*t).

http://www.webassign.net/gianpse3/14-38alt.gif

(a) Find alpha

(b) Find the approximate period of the motion.

(c) Find how long it takes for the amplitude to be reduced to 1/2 of its original value.

Don't I need b to find alpha, since damping force is proportional to dtheta/dt, or F=b(dtheta/dt)?

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# Homework Help: Please Help (damped pendulum)

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