Question

A weight lifter lifts 300 kg from the ground to a height of 2 metres in 3 seconds. The average power generated by the man is
A. 15680 W
B. 3920 W
C. 1960 W
D. 980 W

Answer 1

Hint: Power is the term given to work done by a body or an object in a certain amount of time in the time elapsed. We will find the work done by the weight lifter and then find power. The unit of power is written in watts (W).

Formula Used: \[P = \dfrac{W}{t}\] and W = mgh, where P is average power, W is the work done, t is the time elapsed, m is the mass, g is the acceleration due to gravity, and h is the height.

Complete step by step solution:
We have to find the average power generated by the man. Let the mass lifted by the weight lifter be m, height it was lifted to be h, and time it was lifted in be t.
First, we will find the total work done W by the man using the formula,
\[W = mgh \\
\Rightarrow W = 300 \times 9.8 \times 2 \\
\Rightarrow W = 5880\,J \]
We know that the power is work done in a certain amount of time, so we can find the average power using the formula,
\[P = \dfrac{W}{t} \\
\Rightarrow P = \dfrac{{5880}}{3} \\
\therefore P = 1960W \]

So, option C is the correct answer.

Note: While taking the value of acceleration due to gravity, make sure that you use the accurate value of it, that is \[9.8\,m{s^{ - 2}}\], and not the approximate value, that is \[10\,m{s^{ - 2}}\], as the approximate value is only used for the calculations which might be lengthy, but for simple calculations we have to use the accurate value of acceleration due to gravity.