Question

A boy of mass $40kg$ runs upstairs and reaches the roof at height $8m$ in $5s$. $($Take $g=10m{s}^{-2})$ Calculate the power spent by boy.

• A. $640W$
• B. $6.4KW$
• C. $320W$
• D. None of the above

Answer 1

The correct option is A $640W$

$Force=m\times a$.
Given mass is equal to 40kg and as we are finding force of gravity $a=g$.
Hence $F=40\times 10=400N$.
Here given that displacement is $8m$.
$Work=F\times s$.
Hence $W=400\times 8=3200Joule$.
$Power=Work/time$
$P=3200/5=640W$.