Academic Integrity: tutoring, explanations, and feedback — we don’t complete graded work or submit on a student’s behalf.

physics The pendulum in your grandfather\'s clock comprises a thin bar of length

ID: 3892093 • Letter: P

Question

physics

The pendulum in your grandfather's clock comprises a thin bar of length l and a heavy mass m. The vertical bar can pivot about it's upper end and the mass is attached to the lower end. You exert a small force on the mass in order to start the pendulum swinging. When the mass is at its highest point, the bar makes an angele theta with the vertical. Ignoring the mass of the bar, show that during the time the mass descends from its highest point to its lowest point, the work done by gravity is given by Wg = mgl(1 - cos theta).

Explanation / Answer


at its highest point

cos theta = (l-y1)/l

l* cos theta = l-H

y1 = l*(1-cos theta)

at its lowest point
y2 =0
work done = m*g*(y1-y2) = m*g*l*(1-cos theta)