Hi there!
To solve, we must begin by calculating the total WORK done on the object.
W = F · d (Force · displacement)
Plug in the given values. Remember to convert km to m:
1 km = 1000 m
0.6 km = 600 m
W = 60 · 600 = 36000 J
Now, we can solve for power:
P = W/t
Convert minutes to seconds:
1 min = 60 sec
20 min = 1200 sec
P = 36000/1200 = 30 W ⇒ Choice D.
