A rope 100 feet long weighing 2 pounds per foot hangs over the edge of a building 100 feet tall. How much work in foot-pounds is done in pulling the rope to the top of the building?
A)7500
B)5000
C)1000
D)500
E)10,000
F)750
G)1250
H)12,500

Question

Quizplus · Accepted Answer

The work done in pulling the rope to the top is calculated by integrating the weight of the rope over the distance it is lifted. The weight of the rope is 2 pounds per foot, and the center of mass of the rope is at 50 feet (halfway up). Thus, the work done is 2 pounds/foot * 100 feet * 50 feet = 10,000 foot-pounds.

A Rope 100 Feet Long Weighing 2 Pounds Per Foot