As described in this project’s write-up, “The brachistochrone curve is a classic physics problem, that derives the fastest path between two points A and B which are at different elevations.” In other words, if you have a ramp leading down to another point, what’s the quickest route?

Intuitively—and incorrectly—you might think this is a straight line, and while you could work out the solution mathematically, this rig releases three marbles at a time, letting them cruise down to the Arduino Uno-based timing mechanism to determine the result.  

The ramps are made out of laser-cut acrylic, and the marbles each strike a microswitch to indicate they’ve finished the race. The build looks like a great way to cement a classic physics problem in students’ minds, and learn even more while constructing the contraption!