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a tower outside the houses of parliament in London has a famous clock commonly r

ID: 2182474 • Letter: A

Question

a tower outside the houses of parliament in London has a famous clock commonly referred to as Big Ben, the name of its 13 ton chiming bell. The hour hand of each clock face is 2.7 m long and has a mass of 61.8kg. Assume the hour hand to be a uniform rod attached at one end. (a) what is the torque on the clock mechanism due to the weight of one of four hour hands when the clock strikes noon? the axis of rotation is perpendicular to a clock face and through the center of the clock. (b) what is the torque due to the weight of one hour hand about the same axis when the clock tolls 3:00 AM?

Explanation / Answer

The center of mass is in the middle of the hour hand of Big Bum, that is L=2.7=1.35m, and L is the lever arm in our problem; Torq T=L*mg*sin(b), where b is angle between arm and vector of gravity; At noon b=180° and T=0; at 9 o’clock b=90° and T=1.35*60*9.8