Define work, energy and power. Give the SI units for each of these quantities. A man whose mass is 80 kg climbs up 30 steps of the stairs in 30 s. If each step is 12.5 cm in height, calculate the power used in climbing the stairs, (g = 10 m s^-2)

CBSE Class 9 CBSE Class 9 Science
1

Work : The work done by a constant force is defined as the product of force in the direction of the displacement and the magnitude of the displacement. Its SI unit is joule (J).

Energy : The capacity of a body, animate or inanimate, to do work is termed as energy. Its SI unit is joule (J).

Power : Power is defined as the rate of doing work. Its SI unit is watt.

Given, m = 30 kg,
h = 30 x12.5 cm = 375 cm = 3.75 m,
t = 30 s,
P = ?
Using P = W/t = mgh/t = 30 x 10 x 3.75/30 = 37.5 W