In a pulley system, what force must be applied to balance a 10-pound weight?

In a pulley system, to balance a weight, the force applied must equal the weight to maintain equilibrium. In this case, the weight to be balanced is 10 pounds. Therefore, an applied force of 10 pounds is necessary to counterbalance this weight effectively.

The other choices suggest different magnitudes of force that would either result in the weight moving or fail to provide enough force to maintain balance. For instance, applying 5 pounds would not be sufficient to balance the 10-pound weight, causing it to fall. Similarly, applying 15 or 20 pounds would create an excessive force, leading to an imbalance where the weight would be lifted rather than balanced. Thus, the only option that provides the exact counterbalancing force necessary for equilibrium is 10 pounds.