Question

A 40-kg boy runs up a flight of stairs 4 m high in 4 s. His power output is:

a) 160 W
b) 392 W
c) 40 W
d) 1568 W

Answer 1

The power output of the boy running up the stairs can be calculated using the formula Power = Work / Time. By finding the work done in climbing the stairs and dividing it by the time taken, we can determine the power output. In this case, the power output is 392 W.

Step-by-step explanation:

To calculate the power output, we can use the formula:
Power = Work / Time

Since the boy's power output is the work done (the energy required to climb the stairs) divided by the time taken, we need to find the work done in climbing the stairs. The work done can be calculated using the formula:
Work = Force * Distance

The force exerted on the boy can be determined using Newton's second law:
Force = Mass * Acceleration

In this case, the acceleration is gravitational acceleration, which is 9.8 m/s^2. Therefore, the force exerted on the boy is:
Force = 40 kg * 9.8 m/s^2

Using this force, we can calculate the work done:
Work = Force * Distance = (40 kg * 9.8 m/s^2) * 4 m = 1568 J

Finally, we can calculate the power output:
Power = Work / Time = 1568 J / 4 s = 392 W

Therefore, the correct answer is option (b) 392 W.