Question

A man $M_1$ of mass $80\text{kg}$ runs up a staircase in $15\text{s}$. Another man $M_2$ also of mass $80\text{kg}$ runs up the same staircase in $20\text{s}$. The ratio of the powers developed by them will be

• A. 1
• B. $\frac{4}{3}$
• C. $\frac{16}{9}$
• D. None of these

Answer 1

The correct option is B $\frac{4}{3}$

Since the length of staircase is same, work done to run up the staircase is same

Hence the power will be inversely proportional to time
$\therefore P\propto \frac{1}{t}$
$\Rightarrow \frac{P_1}{P_2}=\frac{t_2}{t_1}$

$\Rightarrow \frac{P_1}{P_2}=\frac{20}{15}=\frac{4}{3}$

Hence option B is the correct answer