A boy, of mass 50 kg, runs up a staircase of 45 steps in 10 s. If the height of each step is 14 cm, find his power. Take g= 10ms-2 ?

Tina Singh • 10.85K Points
Tutor II Physics

Q. A boy, of mass 50 kg, runs up a staircase of 45 steps in 10 s. If the height of each step is 14 cm, find his power. Take g= 10ms-2 ?

(A) 315 ms
(B) 315 W
(C) 337.5W
(D) 310.55 J

Correct Answer - Option(B)

Explanation by: Tina Singh

Given, the mass of the body, m = 50 kg. h is the height, t is the time. g is the acceleration due to gravity which is aproximated to 10 m/s2 ? 
h = 45 × 14 = 630 cm = 6.30 m 
 t = 10 s, g = 10 ms-2 
 Potential Energy = mgh = 50 × 10 × 6.30 = 3150 J.
 (where J is the unit of energy/work which is joules)
 Power = PE / time = Energy / time = 3150 / 10 = 315 watt.
 (watt is the unit of power which is different from units)

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