Pi is an irrational number engineers use in many everyday tasks, including calibrating the speedometer of automobiles. The wheels on a vehicle are circular, so the circumference of the tire, which is the distance it travels each rotation, is equal to pi times the diameter.
Pendulum clocks greatly improve the ability to keep time, according to About.com. The pendulum moves in the arc of a circle, with the arm of the pendulum equal to the diameter. Thus, pi figures into adjusting the clock for accuracy.
Statisticians use pi in solving questions concerning probability. The standard distribution, or bell curve, depends on pi as a constant.
The speed at which a professional baseball pitcher throws a ball depends on the length of his arm and pi. The joints in the arm are pivot points and the length of bone is the radius of a circle.
Pi is useful in calculations concerning waves. Thus, it finds use in light, sound and electronics. It is a part of many different types of entertainment from concerts to music files. It is a part of projectors as well as the screen on a computer. Pi is even involved in the creation of the rainbow, as well as a person's favorite color.