AI Tutor
If you pull a playground swing back and let go, you already know what will happen next without even looking. You know it will rush down, rise on the other side, stop for a split second, and swing right back to you.
When forces act on an object in a regular, steady way, they create a pattern of motion — a movement that repeats in a predictable cycle over time.
Why doesn't the swing just fly away or stop at the bottom on its first try?

The Back-and-Forth Swing

A swing is an everyday example of a pendulum, which is any hanging weight that swings freely back and forth from a fixed pivot.
When you pull the swing up to position A, gravity pulls down on you, while the chains pull along their length, creating an unbalanced force that accelerates you downward toward the center.
At the lowest point (the center), you are moving at your fastest speed, so your motion carries you right past the middle and up toward position B until gravity slows you to a stop and pulls you back again.
In 1583, Italian scientist Galileo Galilei timed a swinging cathedral lamp using his own pulse, discovering that each complete swing takes the exact same amount of time regardless of how wide it swings.
One complete back-and-forth movement — from left, to right, and back to left — is called a single cycle or period.
Do all repeating patterns of motion move back and forth like a swing?

Three Common Motion Patterns

Forces can produce several distinct patterns of motion depending on how and where the forces push or pull.