Question

A boy of mass 50kg runs up staircase of 45 steps in 9s if the height of each step is 15 cm find his power take g = 10m s

Answer 1

Total displacement = 45*15 = 675 = 6.75 m
Thus, we have, P = W/t = FS/t = (ma)S/t = (50*10*6.75)/9 = (50*10*675)/(9*100) = (5*1*675)/9 = 5*75 = 375 watt
Thus, the boy's power is 375 watt.

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Answer 2

Explanation:

Weight of boy, mg = 50kg × ${10m/s}{2}10m/s2$

= 500N

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Height of the staircase,h = 45 × $\frac{15}{100}$

= 6.75m

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Time taken to climb, t = 9s

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= $power = \frac{work \: done}{time \: taken}power$

= $\frac{mgh}{t}$

= $\frac{500N \times 6.75m}{9s}$

= 375W