Pysical science question on efficiency???

Question

It takes 1200J of work to lift the car high enough to change a tire. How much work must be done by the person operating the jack if the jack is 25 percent effecient?

A windmill has an effeciency of 37.5 percent. If a gust of wind does 125J of work on the blades of the windmill, how much output work can the windmill do as a result of the gust?

Please WORK OUT THANKYUO

Answer 1

Efficiency = what you get out / what you put in.

For the jack problem you need to get 1200 J.

.25 = 1200 J / W

Solve for the work done, W

For the windmill problem, the wind did 125 J of work.

.375 = W / 125 J

Solve for the output work W