Question

A boy of weighing 40 kgf climbs up a stair of 30 steps, each 20 cm high in 4 minutes and a girl weighing 30 kgf does the same in 3 minutes.
Compare :
(i) the work done by them, and
(ii) the power developed by them.

April 9, 2024

Answer

(i) We know that work done is a product of force and displacement

W = F x S = mgh

Given,

m₁ = 40 kgf

m₂ = 30 kgf

t₁ = 4 min = 4 × 60 =240 sec

t₂ = 3 min = 3 × 60 = 180 sec

h₁ = h₂ = 30 × 20 = 600 cm = 6 m

(i) Work_boy : Work_girl = m₁gh₁ : m₂gh₂

= m₁ : m₂

= 4 : 3

Therefore,

Work done by boy : Work done by girl = 4 : 3

(ii) The power developed —

We know that,

Power = $work\over Time$

Power_boy : Power_girl = $40 × 10 × 6\over 240$ : $30 × 10 × 6\over 180$

= $2400\over 240$ : $1800\over 180$

= 10 : 10 = 1 : 1

Power developed by boy : Power developed by girl = 1:1.

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Question

A boy of weighing 40 kgf climbs up a stair of 30 steps, each 20 cm high in 4 minutes and a girl weighing 30 kgf does the same in 3 minutes. Compare : (i) the work done by them, and (ii) the power developed by them.

Answer

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Flash Education

A boy of weighing 40 kgf climbs up a stair of 30 steps, each 20 cm high in 4 minutes and a girl weighing 30 kgf does the same in 3 minutes.
Compare :
(i) the work done by them, and
(ii) the power developed by them.