The parabola appears when graphing a quadratic equation, which in its basic form can be written as y=x^2. The shape occurs naturally in the physical world. Humans also use parabolic shapes when designing objects ranging from bridges to satellite dishes.

## Free Flight

A popular example of a parabola in the real world is the trajectory of a ball in free flight. As you throw a ball, it first goes up and forward, then falls down while continuing to travel forward, thus forming an inverted parabola path. A parabolic motion also occurs when a basketball bounces on a hard floor. Another example is a baseball hit by a batter.

## Rotating Liquid

When liquid is rotated, the forces of gravity meet the centrifugal force, which results in the liquid forming a parabola-like shape. The most common example is when you stir up orange juice in a glass by rotating it round its axis. The juice level rises round the edges while falling slightly in the center of the glass (the axis). Another example of rotating liquids is the whirlpool.

## Reflector

Parabola is also used in satellite dishes and flashlights. In satellite dishes it helps reflect signals that then go to a receiver, which interprets the signals and shows satellite-transmitted channels on your TV. In flashlights, automobile headlights and spotlights, parabolic shape helps reflect light.