Posted by **peter** on Friday, December 2, 2011 at 11:22am.

I don't know where to begin with this question. Could someone help me please?

A rod of mass 4.1 kg and length 1.6 m hangs from a hinge as shown in the figure below. The end of the rod is then given a "kick" so that it is moving at a speed of 5 m/s. How high will the rod swing? Express your answer in terms of the angle the rod makes with the vertical.

- college physics -
**drwls**, Friday, December 2, 2011 at 11:38am
The angular momentum of the rod right after the kick is given by

I*w = (1/3)M*L^2*w

where w = ( 5 m/s)/L = 3.13 rad/s

I*w = 10.95 kg*m^2/s

Next, compute the total kinetic energy at the start of the upward swing.

KE(max) = (1/2)*(I*w)*w

That equals the increase in potential energy at maximum deflection angle A. That angle is determined by the center of mass location.

Check my thinking. I am leaving the rest up to you.

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