A: Yes, pendulum sights do work out to about 30 yards, plus or minus, depending on arrow trajectory. They use a real-world trigonometric formula to compensate for arrow drop at varying ranges via a swinging sight pin. It sounds complicated, but actually it is harder to describe than to understand if you see one in action. Once the stationary pin is sighted in at a given range, it is allowed to "swing" freely under gravity. The only catch is the archer must shoot from an elevated position—usually higher than 10 feet—for the pendulum to swing and the formula to work. As the bow is raised or lowered for elevation, the sight pin remains on target.
When a long-range shot—usually more than 30 yards—necessitates holding much over the target, the sight bottoms out and is no longer effective. Pendulum sights are extremely useful when hunting predominately from tree stands because they eliminate perhaps the toughest element of bow shooting—range estimation.