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ICSE Class 10 Physics Question 1 of 20

Solved 2016 Question Paper ICSE Class 10 Physics — Question 2

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Question

Question 1(b)

A boy weighing 40 kgf climbs up a stair of 30 steps each 20 cm high in 4 minute and a girl weighing 30 kgf does the same in 3 minutes. Compare :-

(i) The work done by them.

(ii) The power developed by them. [2]

Answer

(i) The work done by them = ?

While climbing both the girl and boy have to do work against the force of gravity.

Force of gravity on boy = F1 = m1g = 40 x 10 = 400

Force of gravity on girl = F2 = m2g = 30 x 10 = 300

Total height climbed up

h = number of steps x height of each step

= 30 x 20 = 600 cm = 6 m

Work done by the boy = W1 = F1 x h = 400 x 6 = 2400 J

Work done by the girl = W2 = F2 x h = 300 x 6 = 1800 J

Therefore, W1 : W2 = 2400 : 1800 = 4 : 3

(ii) The power developed by them = ?

P1P2=W1t1W2t2=W1W2×t2t1=43×34=1:1\dfrac{P_1}{P_2} = \dfrac{\dfrac{W_1}{t_1}}{{\dfrac{W_2}{t_2}}} \\[0.5em] = \dfrac{W_1}{W_2} \times \dfrac{t_2}{t_1} \\[0.5em] = \dfrac{4}{3} \times \dfrac{3}{4} \\[0.5em] = 1 : 1