Gravitational Illusion Ball Ramp

Scientific curiosity come to life

As every schoolchild and budding physicist knows, the shortest distance between two points is a straight line—or is it? This wooden desktop demonstration is one of a series I call Gravitational Illusions. It’s a simple build comprising two ramps, one straight and one wavy, surrounded and separated by thin hardwood walls. At the end is a box to catch the 5/8" diameter steel ball bearings. But the simplicity of the build belies the complexity of the question: when released at the same time, which ball will reach the ramps’ end first?

There are three possible answers. The ball on the right has the shorter, straighter path, so maybe it gets there first. The ball on the left has a longer path but a steeper start, so maybe it gets there first. Or, since both balls start and end at the same height, maybe they get there at the same time. Throw together this little curiosity and test your own theory – or inspire a young budding physicist.

Construction notes

Copy the pattern on this page (or download it from our website and print it out). Adhere it to a length of 3/4” thick stock using spray adhesive. Bandsaw the ramp to shape and sand the wavy edge smooth at the spindle sander. Lay out a 7° ramp on a second piece of milled stock and cut to shape. Mill the base and frame pieces, then glue the assembly together as shown below. Then puzzle friends and family over which ball will win the gravity-fueled race to the bottom!


Photos: Doug Loyer | Illustrations: Michael Church

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