(i) Define power. Mention its SI unit. (ii) A boy of mass 50 kg runs up a staircase of 40 steps in 8 s. If the height of each step is 15 cm, find his power. (Given, g = 10 m s^-2)

CBSE Class 9 CBSE Class 9 Science
1

(i) Power is defined as the rate of doing work or rate of transfer of energy. Its SI unit is watt.

(ii) Given m = 50 kg,
h = 40 x 15 cm = 600 cm = 6 m,
t = 8 s,
P =?
Using P = W / t = mgh / t
= 50 x 10 x 6/ 8 = 375 W.