Question

A man of mass $80kg$ carrying a load of $20kg$ walks up a stair case in $20s$. If the number of steps is $40$ and width and height of each step are $20cm$ and $15cm$ respectively. The efficiency of the man is

• A. $20\%$
• B. $25\%$
• C. $40\%$
• D. $50\%$

Answer 1

The correct option is A $20\%$

$\begin{array}{c}\text{mass of man}M=80kg\\ \text{mass of load}m=20kg\\ \text{as number of steps}40\%\text{width}\varphi \\ \text{height respectively iscm \&}20cm\\ \text{work done for load}=(20\times 40\times 0.2)J\\ \text{work done for}man=(80\times 40\times 0.2)J\end{array}$

$\begin{array}{c}=\frac{(20\times 40\times 0.2)}{(80\times 40\times 0.2)}\times {100}^{\circ })\\ =20\%\end{array}$

Answer: A