Amover 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

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.