Question

What is the power generated by a 45 kg person who walks up a flight of 12 stairs, each 30 cm high, in 12 s?
A.13.5 W
B.132.3 W
C.1,350 W
D.13,230 W

Answer 1

The total distance covered by the person is 12 times the height of each stair:
$\Delta h=12 \cdot 30 cm=360 cm=3.60 m$

The work done by the person to climb the stairs is equal to the increase in his gravitational potential energy:
$W= \Delta U=mg \Delta h=(45 kg)(9.81 m/s^2)(3.60 m)=1589.2 J$

And therefore, the power generated by the person in 12 s is the work done divided by the time taken:
$P= \frac{W}{t}= \frac{1589.2 J}{12 s}=132.3 W$

So, the correct answer is B.