Question

A man weighing 500 N carried a load of 100 N up a flight of stairs 4 m high in 5 seconds. What is the power?

Answer 1

Weight of the man, (W₁) = 500 N
Weight of the load, (W₂) = 100 N
Height, (h) = 4 m
Time taken, (t) = 5s
So total weight,
W = W₁ + W₂
= (500 + 100) N
= 600 N
We can calculate the work done against gravity as,Work done by the man is = (total weight)(vertical distance)
= (600)(4)
= 2400 J
Now, we can calculate the power of the man as,
$$\begin{gathered} \mathrm{Power}=\frac{\mathrm{Work}\mathrm{done}}{\mathrm{Time}} \\ \mathrm{So}, \\ \mathrm{Power}=\frac{2400}{5}\mathrm{W} \\ =\boxed{480\mathrm{W}} \end{gathered}$$
So, the power of man is 480 W.