How many 2kg bricks can a man carry up a staircase 1m high in two hours if he works at the average rate of 19.6watts?

Given, 

Mass, m = 2 kg

Height, h = 1 m

Time, t = 2hour = 60 x 60 sec = 3600 sec

Power, P = 19.6 watts

No. of bricks, n = ?

We know that, $P=\frac{W}{t}$ ,

where P = power, W = work done by an object or body and t = total time taken.

$P=\frac{mgh}{t}$ $[\because W=mgh]$

where P = power, m = mass of an object or body, g = acceleration due to gravity, h = height/distance and t = total time taken.

Therefore, to find no. of bricks we multiply it in the power formula,

$P=\frac{n\times mgh}{t}$

Putting the given values in the above expression we get-

$19.6=\frac{n\times 2\times 9.8\times 1}{2}$   $[\because g=9.8m/{s}^{2}]$

$19.6\times 2=n\times 2\times 9.8\times 1$

$39.2=19.6\times n$

$n=\frac{39.2}{19.6}$

$n=2$

Hence, no. of bricks that a man carry is 2.

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Updated on: 10-Oct-2022

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