Question

A boy of mass 40 kg runs up a flight it of 50 steps, each
of 10 cm high, in 5 s. Find the power developed by the
boy​

Answer 1

Answer:

Here,

mass of boy = 40kg

total height gained h = 50×10 = 500 cm = 5m

time taken to climb = 5 sec

work done by boy,

w = mgh

=> 40kg × 10× 5m

=> 2000j

power developed ,

$p = \frac{w}{t}$

$= > \frac{2000j}{5s}$

$= > 400w$

Answer 2

Answer: 400 watt.

Explanation:

Given,

Mass of  boy (m) = 40 kg

Number of Steps = 50

Since each step is 10 cm in height there fore,

50 Steps = 10 × 50 = 500 cm = 5m.

Therefore displacement of boy in upward direction(h) = 5m

Now  gravity works in downward direction and boy has to work against gravitational force that is potential energy at height h = 5m

So,

Work done by boy = mgh

                               = 40 × 10 × 5

                               = 2000 Joule.

Since this work is done in the time t = 5 second.

So we know that,

Power = Work Done/Time Taken

Power = 2000/5

Power = 400 watt.

So the power developed by the boy will be 400 watt.