## College Physics (4th Edition)

We need to pull down on the rope with a minimum force of $480~N$
Let $T$ be the tension in the rope. From the diagram of the lower pulley, we can see that at constant velocity, $2T = mg$, where $mg$ is the weight of the box. Then: $~T = \frac{mg}{2}$ To keep the box moving with a constant velocity, we need to pull on the rope with a minimum force of $T$: $T = \frac{mg}{2}$ $T = \frac{(98.0~kg)(9.80~m/s^2)}{2}$ $T = 480~N$ We need to pull down on the rope with a minimum force of $480~N$