Question

A student weighing 700 N climbs at constant speed to the top of an 8 m vertical rope in 10 s. The average power expended by the student to overcome gravity is most nearly
(A) P = 560 W.
(B) P = 87.5 W.
(C) P = 5,600 W
(D) P = 1.1 W.
(E) P = 875 W

Answer 1

To solve this problem we will use the concepts related to power, defined as the amount of energy applied over a period of time.

The energy in this case is the accumulated in the form of potential energy, over a period of time. Thus we will have that the mathematical expression of the power can be expressed as

$P = \frac{E}{t}$

Here,

E = Energy

t = time

As the energy is equal to the potential Energy we have tat

$P = \frac{mgh}{t}$

The weight (mg) of the man is 700N, the height (h) is 8m and the time is 10s, then:

$P = \frac{700*8}{10}$

$P = 560W$

Therefore the correct answer is A.