Potential Well

Orbital motion simulated by ball rolling on wooden potential well.

What it shows:

Motion in a central potential is demonstrated by a ball rolling on a circular 1/r curved surface.

How it works:

The 1/r potential well simulates the gravitational potential surrounding a point mass; a ball bearing moving in this potential follows a parabolic or elliptical orbit depending upon its initial trajectory and velocity. As it loses energy due to friction, the orbit decays and the ball spirals towards the centre of the well. You could also think of this surface as a curved space geometry for a point source.

potential well

Setting it up:

It is important to level the potential well, well. A 1" diameter metal ball bearing gives the best results.


This maple wood potential surface was crafted by Nathaniel P. Carleton for Harvard at the time of the Sputnik 1 launch. A beautiful job, but it can be difficult to get a nice orbit. Practice first, either with this or with a roulette wheel. Commercially available potential wells, usually of fibre glass, are available from [ ]. A good accompaniment would be the gravitational field surface demo.