A

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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)
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  • Filed under category Physics
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Explanation by: Admin

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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