Cycloid

A vertical purple information panel, with two clear tubes that contain a red and yellow ball.
A tall and short purple vertical panels joined together by black steel bars and two metal ball tracks.

The fastest path between two points isn’t always a straight line.

How it works

Race two balls down two separate tracks: one straight track (which appears to be shorter) and one curved or cycloid track (which appears to be longer).

Things to try or ask around the exhibit

Which ball will ‘win the race’ to reach the end first?

Background

The curved track is cycloid-shaped. A cycloid gives the best trade-off between getting the ball moving quickly (on the steep slope near the start) and making the trip as short as possible.

You can trace a cycloid path by following a point on the rim of a bicycle wheel as it rolls long. Teeth on gears are often cycloid-shaped to help them mesh smoothly.