Question

A boy of 50 Kg runs up a staircase of 45 steps in 9 secs. If the height of each step is 15 cm, his power is (taking g = 10 ms⁻²)
a. 375 W
b. 500 W
c. 37.5 W
d. 3.75 W

{AMU +2 ENTRANCE TEST 2012-13}

Answer 1

HELLO DEAR,
MASS OF THE BOY IS 50 KG


AND THE HEIGHT= H


=> 15×45=675 CENTIMETRES

=> 675/100 meter


AND TIME =9 SECOND



WE KNOW THAT THE,


POWER =WORK/TIME

=>MGH/T

$\frac{50 \times 10 \times 675}{9 \times 100} = \frac{50 \times 10 \times7 5}{100} \\ = > 375watt \: \\ \: i \: hope \: its \: help \: you \: dear$

Answer 2

Hey Rehan and others.....

Height of one step = 15cm

height of 45 steps = 15 × 45 cm = 15 × 45 /100 m [ in SI unit ]

Mass of the boy = 50 Kg

g = 10m/s

time taken to run up = 9 seconds...
Work done = m × g × h

so, Power = mgh/t....


Power = 50× 10 × 15 × 45 / 100 × 9

= 375 W

so your answer is Option (a)


Hope it helps