Final answer:
The gyro instrument that operates on the principle of precession is the gyroscope. Gyroscopes resist changes to their orientation due to angular momentum, and when a perpendicular torque is applied, they precess instead of tipping over. This principle is vital for navigational instruments in vehicles like airplanes and spacecrafts.
Step-by-step explanation:
The gyro instrument that works on the principle of precession is known as the gyroscope. Precession is the phenomenon where the axis of a spinning object, like the gyroscope, moves in a cone-like motion in response to a torque that is applied perpendicular to the object's angular momentum. This principle is widely used in navigational instruments, particularly in airplanes and spacecrafts to maintain orientation.
When a gyroscope spins, it resists changes to its orientation due to its angular momentum. However, when a torque is applied, such as from gravity when the gyroscope's axis is not vertical, the gyroscope does not simply tip over. Instead, it precesses, meaning it rotates about a vertical axis, with the rate and direction of this precession depending on the applied torque and the angular momentum of the gyroscope.
To illustrate, consider a gyroscope spinning with its axis not perfectly vertical. Due to the force of gravity, a torque acts on the center of mass creating a force that would typically make it fall over. But if the gyroscope is already spinning, this force instead causes it to precess around a vertical axis, maintaining its balance. Earth itself can be considered a massive gyroscope with its angular momentum pointing towards Polaris, the North Star, and undergoing precession.