Spring pendulum

A spring pendulum is a type of simple machine made up of a weight (called a bob) attached to a spring. When the spring is pulled down and released, the weight swings back and forth in a pendulum-like motion. Because of the way the spring is attached, the bob always comes to rest at the same point before it swings back in the opposite direction. This makes it a great way to demonstrate the laws of motion, since it shows how energy is able to transfer back and forth.