A girl pushes a merry-go-round with a force of 120N for a distance of 6.0m.

Question

a) if she does this over a span of 2 seconds, how much power does she exert?
b)if the merry-go-round gains a kinetic energy of 500J, what is the girls efficiency?

Answer 1

a) To determine the power exerted by the girl, we use the formula:

Power = Work / Time

First, let's calculate the work done by the girl. The work done is given by the formula:

Work = Force * Distance

So, Work = 120 N * 6.0 m = 720 J

Now, let's calculate the power:

Power = 720 J / 2 s = 360 W

Therefore, the girl exerts 360 Watts of power.

b) Efficiency is given by the formula:

Efficiency = (Useful energy output / Total energy input) * 100%

The useful energy output in this case is the kinetic energy gained by the merry-go-round, which is given as 500 J.

The total energy input is the work done by the girl, which is 720 J.

So, Efficiency = (500 J / 720 J) * 100% = 69.44%

Therefore, the girl's efficiency is approximately 69.44%.