Question

$\begin{array}{c}\text{A man weighing}80kg\text{climbs a staircase}\\ \text{carrying a}20kg\text{load. The staircase has}40\\ \text{steps, each of}25cm\text{height. If he takes}20\\ \text{seconds to climb, the work done is}\end{array}$

• A. $9800J$
• B. $245J$
• C. $98\times {10}^{4}J$
• D. 7840 J

Answer 1

The correct option is B $245J$

As the man climb up the stair he does the work against the gravity$,$ the total gravitational force act on it in downward direction $=(80+20)g$

here $g$ is the acceleration due to gravity$,$

height raised by the man $25cm=0.25m$

work done by the man $\left(80+20\right)\times g\times 0.25=245J$

Hence,

option $\left(B\right)$ is correct answer.