Question

Consider a 30-foot chain that weighs 4 pounds per foot hanging from a winch 30 feet above ground level. Find the work done by the winch in winding up the entire chain.

Answer 1

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Answer:

1800 ft·lb

Explanation:

The weight of the chain is ...

(4 lb/ft)(30 ft) = 120 lb

The center of mass of the hanging chain is its midpoint, 30/2 = 15 ft below the winch. The work done winding the chain is the work done lifting the center of mass 15 ft to the winch:

(120 lb)(15 ft) = 1800 ft·lb