A boy, who weighs 50 N, runs up a flight
of stairs 6.5 m high
in 7 seconds.
How much power does
he develop?
A 6.5 / (50 x 7) W
B (7 x 6.5) / 50 W
C 50 / (7 x 6.5) W
D (50 x 6.5) / 7 W
Correct Answer: D
Explanation: Here,
Weight of the boy, w = 50 N
Height of the stairs, h
= 6.5 m
Time taken, t = 7 s
Power developed, p =
(work done / time taken)
= [(weight x height) / time taken]
= [(50 N x 6.5 m) / 7 s]
= (50 x 6.5) / 7 W
Hence the correct answer
is D.
