Final answer:
A flyball governor is an example of a gravity-controlled centrifugal governor designed to regulate the speed of steam engines by using centrifugal force and gravity.
Step-by-step explanation:
The flyball governor is an example of a gravity-controlled centrifugal governor. This device was invented by James Watt to regulate the speed of steam engines. As engine speed increases, centrifugal force pushes the flyballs outward, lifting a sleeve which connects to the engine's throttle. Gravity works against this centrifugal force to bring the balls back towards the centre when the speed decreases, thus lowering the sleeve and increasing the engine's speed. This feedback system helps to maintain a constant engine speed. There are various types of governors, however, the flyball governor is specifically designed to utilize the opposing forces of centrifugal force and gravity.
Pendulum governors, sleeve governors, and inertial governors are other forms of governors, but they operate on different principles and are not necessarily controlled by the force of gravity in the way the flyball governor is.