[amp_mcq option1=”400 watts” option2=”500 watts” option3=”4000 watts” option4=”None of these” correct=”option1″]
The correct answer is A. 400 watts.
The power developed by the boy is given by:
$P = \frac{W}{t}$
where $W$ is the work done and $t$ is the time taken.
The work done in climbing up the rope is given by:
$W = mgh$
where $m$ is the mass of the boy, $g$ is the acceleration due to gravity, and $h$ is the height of the rope.
The height of the rope is given by:
$h = 8 \text{ m}$
The mass of the boy is given by:
$m = 50 \text{ kg}$
The acceleration due to gravity is given by:
$g = 9.8 \text{ m/s}^2$
Therefore, the work done in climbing up the rope is:
$W = (50 \text{ kg})(9.8 \text{ m/s}^2)(8 \text{ m}) = 3920 \text{ J}$
The time taken to climb up the rope is given by:
$t = 10 \text{ s}$
Therefore, the average power developed by the boy is:
$P = \frac{3920 \text{ J}}{10 \text{ s}} = 392 \text{ W}$
Since the options are given in multiples of 100, we can round 392 to 400. Therefore, the correct answer is A. 400 watts.
Option B is incorrect because it is twice the actual power. Option C is incorrect because it is 10 times the actual power. Option D is incorrect because it is not a possible value of power.