Question

A boy of mass 60 kg runs up a staircase of 45 steps in 9 s. If the height of each step is 15 cm, find his power. Take g = 10 m s–2NCERT Class IXSciences - Main Course BookChapter 11. Work and Energy

Answer 1

m= 60kg

h= 45 x 15= 675m

g= 10m/s^2

Work= mgh

        = 60 x 675 x 10

        = 405000

Power= Work/ Time

          = 405000/9

          = 45000W

Therefore, his power is 45000 watts.

Answer 2

Answer:

Given mass of body (m)=50kg

h=45×15=675cm=6.75m

t=9s    δ=10m

Potential energy =mgh

                             =(50×10×6.75)5

                             =33755

Power of the body =TimePotentialenergy

                                =93375

                                =375W Answer