Question

A boy of mass $50$ kg runs up a staircase of $45$ steps in $9$ s. If the height of each step is $15$ cm, fimd his power. Take $g=10m{s}^{-2}$.

Answer 1

Since, each step of stair case denotes $15$cm

So, total height$\left(h\right)$ of $45$ steps$=45\times 15$

$=675$cm

$=6.75$m

Work done by the boy$=$wt$\times$height

$w=mg\times h$

$=50\times 10\times 6.75$

$w=3375$J

We know that,

Power$\left(P\right)=\frac{workdone\left(w\right)}{Timetaken\left(T\right)}$

$\Rightarrow$ Power$=\frac{3375}{9}J{s}^{-1}$

Power$=375$w or $J{s}^{-1}$.