Question

A girl of mass 40 kg runs up a staircase of 30 steps in 10 s. If the height of each step is 0.1 m, find the power developed by her. Take g = 10 \small ms^{-2}

112 W
1200 W
120 W
133 W​

Answer 1

Explanation:

Explanation:A girl of mass 40 kg runs up a flight of 15 steps each 15 cm high in 10 s. Find: (i) the work done and (ii) the power developed by him Take g = 10 N kg-1

Explanation:A girl of mass 40 kg runs up a flight of 15 steps each 15 cm high in 10 s. Find: (i) the work done and (ii) the power developed by him Take g = 10 N kg-1Force of gravity on boy F= mg = 40 × 10 = 400N Total distance covered in 15 steps , S = 15 × 15cm = 225cm = 2.25m Work done by the boy in climbing = Force x distance moved in direction of force Work, W = F × S = 400 × 2.25 = 900J Power developed = work done/time takrn = 900J/10s = 90W

Answer 2

Given:

A girl of mass 40 kg runs up a staircase of 30 steps in 10 s

To find:

the power developed by the girl

Solution:

It is given that the girl is climbing the stairs so the work done by the girl will be given by:

Work = mgh

where

m = 40 kg

g = 10 m/sec²

h = 0.1 × 30 = 3 m

Work = 40×10×3

Work = 1200 joules

and the power developed by the girl is given by:

Power = work/time

Work = 1200 J

Time = 10 sec

Power = 1200/10

Power = 120 Watt

Hence, the power developed by the girl 120 W