A man lifts a 20.0-kg bucket of concrete from the ground up to the top of a 20.0-m tall building. The bucket is initially at rest, but is traveling at 4.0 m/s when it reaches the top of the building. How much work was done by the man in lifting the bucket?

Question

Quizplus · Accepted Answer

The work done by the man can be calculated using the work-energy principle, which states that the work done on an object is equal to its change in kinetic energy. The initial kinetic energy of the bucket is zero, so the work done by the man is equal to the change in potential energy of the bucket:

W = mgh

where W is the work done, m is the mass of the bucket (20.0 kg), g is the acceleration due to gravity (9.81 m/s^2), and h is the height moved (20.0 m). Plugging in the numbers:

W = (20.0 kg)(9.81 m/s^2)(20.0 m) = 3,920 J = 3.92 kJ

Therefore, the best answer choice is D.

A Man Lifts a 20