Question

Coolie $\text{A}$ takes 1 $\text{minute}$ to raise a box through a height of $2\text{m}$. Another coolie $\text{B}$ takes $30\text{sec}$ for the same job and does the same amount of work. Choose the correct option.

• A. Coolie $\text{A}$ exerts more power than coolie $\text{B}$
  
• B. Coolie $\text{B}$ exerts more power than coolie $\text{A}$
• C. Coolie $\text{A}$ exerts same power as coolie $\text{B}$
  
• D. None of the above
  

Answer 1

The correct option is B Coolie $\text{B}$ exerts more power than coolie $\text{A}$

Power of cooile $\text{A}$

$=\frac{Work}{Time}=\frac{M\times g\times S}{t}=\frac{M\times g\times 2}{60}J/s$

Power of coolie $\text{B}=\frac{M\times g\times 2}{30}J/s$

Clearly, the power of coolie $\text{B}$ is twice the power of coolie $\text{A}$

For the same work,

$W=p_1{t}_1=p_2{t}_2$

or,
$\frac{P_2}{P_1}=\frac{t_1}{t_2}=\frac{1minute}{30s}=2\Rightarrow P_2=2P_1$

In other words, $P_B=2P_A$

Why this Question? Tip: The average power is defined as the rate of work done per unit time. $W=P_{avg}t$