What happens to a balloon when it reaches an altitude where the upward buoyant force equals the downward weight?

When a balloon reaches an altitude where the upward buoyant force equals the downward weight, it remains suspended in equilibrium. At this point, the forces acting on the balloon are balanced. The buoyant force, which is the upward force exerted by the surrounding air, counteracts the weight of the balloon pulling it downward. As a result, there is no net force acting on the balloon, causing it to stop ascending and remain at that altitude.

This situation is similar to how objects behave when they reach their neutral buoyancy in water; they neither sink nor float to the surface but remain suspended. If the buoyant force were to increase or decrease due to changes in the air density or the balloon’s weight, the balloon would either rise or fall accordingly.