Question

a boy of mass 50kg runs up a staircase of 45 steps in 9seconds.if the height of each step of the staircase is 15cm,find the power of the boy (g=10ms-2 ) step by step

Answer 1

m=50kg; a=g=10m/s;
F=500N. S=45×0.15=6.75m;
W=F.dr=500×6.75=3375J
P=W/T=3375/9=379W or J/s

Answer 2

Answer:

The power is 375 W.

Explanation:

Given,

A boy of mass (m) = 50 kg

No. of steps = n = 45

Time taken (t) = 9 s

Height of each step = 15 cm = 15 / 100 m

To find: find his power

Solution:

Concept involved:  Power is the rate of doing work.

Total height of staircase = No. of steps * height of each step

or, Total height of staircase = 45 * 15 / 100 = 6.75 m

Work done would be equal to the Potential Energy possessed by the body.

i.e W = mgh

here, m = 50 kg , g = 10 m/s^2, h = 6.75 m

Substituting the values,

W = 50*10*6.75

And, Power = work done / time

or, P = W / t

or, P = 50*10*6.75 / 9

or, P = 375 W

Therefore, The power is 375 W.