Question

A 110-pound seafarer walks up a flight of stairs 12.8 m high in 45 seconds. How much power did he used?

Answer 1

The work done by seafarer is equal to his potential energy gain:

$$W = mgh$$

where $m = 110lbs \approx 49.9kg$ is his mass, $h = 12.8m$ is the height of the stairs, and $g = 9.81N/kg$ is the gravitational acceleration.

By definition the power is the work done in unit time:

$$P = \dfrac{W}{t}$$

where $t = 45s$ is the time.

Thus, obtain:

$$P = \dfrac{mgh}{t}\\ P = \dfrac{49.9\cdot 9.81\cdot 12.8}{45} \approx 140W$$

Answer. 140 W.