Question

A man weighing $80kg$ climbs a staircase carrying a $20/kg$ load. The staircase has $40$ steps, each of $25cm$ height. If he takes $20seconds$ to climb, the work done is (Take $g=10m/s^2$):

• A. $9800J$
• B. $490J$
• C. $98\times {10}^{5}J$
• D. $7840J$

Answer 1

The correct option is A $9800J$

Gravity is a conservative force so W.D is independent of path followed

$m$ is total mass ( load plus man ). $h$ is the total height.
Work done: $W=mgh=100\times 9.8\times (40\times .25)=9800J$