Question

A man weighing $80$kg climbs a staircase carrying a $20$kg load. The staircase has $40$ steps, each of $25$cm height. If he takes $20$ seconds to climb, the work done is?

• A. $49$W
• B. $40$W
• C. $98\times {10}^5$J
• D. $7840$J

Answer 1

Answer: (A)

$Potentialenergy=mass\times accelerationduetogravityx-height$
$P.E.=m\times g\times h$
According to the given condition -
$m=80+20=100kg$
$g=9.8m/s^2$
$h=25\times 40=1000cm=1m$
$P.E=WorkDone=100\times 9.8\times 1=980J$
Power is rate of work done =$\frac{WorkDone}{TimeTaken}=\frac{980}{20}=49J/s=49$Watt