A mover uses 1250 J of energy to move a 25 kg box up an inclined plane to a height of 4 m. What was the mover's efficiency while moving the box?

0.784

Explanation:

Efficiency is the ratio of energy out over energy in.

We know the energy in was 1250 J.

The energy out is the change in potential energy of the box:

PE = mgh

PE = (25 kg) (9.8 m/s²) (4 m)

PE = 980 J

So the efficiency is:

e = 980 J / 1250 J

e = 0.784