A bridge worker needs to pull a 10-meter uniform cable with mass 3 kg/meter up to the work platform.A second worker needs to pull an identical cable (which is one-half as long)up one-half the original distance.Will the second worker do one-half the work of the first worker? Assume that each cable is hanging straight down from its platform.

Question

Quizplus · Accepted Answer

The work done to lift a cable is directly proportional to both the mass of the cable and the height it is lifted. Since the second cable is half as long and only lifted half the distance, its mass is half that of the first cable, and it is lifted half as far. However, work is calculated as force times distance. The force needed is directly proportional to the mass, so halving the mass and the distance results in one-quarter the work done, not half.

A Bridge Worker Needs to Pull a 10-Meter Uniform Cable