Awanita is placing items on a shelf that is 200 cm above the ground. She exerts a force of 20 N to lift a box from the floor to the shelf. She does this in 5 s.

What is Awanita's power output? (Power: P = W/t)

4 W

8 W

40 W

800 W

The answer is 8 W

P = ?

P = W/t

P - power, W - work, t - tim

We have t (t = 5s), but we need to calculate work W:

W = F * d

F - force, d - distance

We know that:

F = 20 N

d = 200 cm = 2 m

W = F * d = 20 N * / 2 m = 40 J

Now when we know W and t, we can calculate power P:

P = W/t

W = 40 J

t = 5 s

P = 40 J / 5s = 8 W