Question

A girl of mass 42 kg runs up a flight of 60 steps each of 15 cm height in 12 second. calculate a. The work done by her, b. The power developed (take g= 10m/s²)​

Answer 1

Mass of the girl (m) = 42 kg

Number of steps of flight (n) = 60

Height of each step (h) = 15 cm

Total height (H) = 60 × 15 = 900 cm = 9 m

Time taken (t) = 12 s

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★ Work Done (W) : Work done by the body is given by the force exerted on the body in the direction of displacement

➙ W = F × s

➙ It is a scalar quantity having only magnitude

➙ SI units : Joule

★ Power (P) : Power developed by the body is given by the work done per unit time

➙ P = W / t

➙ It is a scalar quantity having only magnitude

➙ SI units : Watt

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➠ W = F × s

➠ W = m × g × H

➠ W = (42)(10)(9)

➠ W = 3780 J  $\pink{\bigstar}$

Work done by her = 3780 J

➳ P = W / t

➳ P = 3780 / 12

➳ P = 315 W  $\green{\bigstar}$

Power developed by her = 315 W

Answer 2

Given :

A girl of mass 42 kg runs up a flight of 60 steps each of 15 cm height in 12 second

　

To find :

1. The work done by her,
2. The power developed (take g= 10m/s²).

　

Using formulas :

1) W = m × g × h.

2) P = W/t.

　

Calculations :

→ Work done = 42 × 10 × 9

→ Work done = 3,780 J

　

→ Power = 3780/12

→ Power = 315 W

　

Therefore,

1. Work done by her = 3,780 Joule.
2. Power developed by her = 315 Watt.