The Newtonian Demonstrator, known today as the Newton's Cradle, is a device that demonstrates the laws of conservation of momentum and energy. The concept was demonstrated centuries ago in France and used by Sir Isaac Newton when he developed the laws of physics.
How the Newton's Cradle works
When the first ball strikes the row of balls, the impact produces a shock wave that travels through the metal balls at the speed of sound. The speed of sound through steel is much faster (4699 m/s) than through air (300 m/s). The time for the shock wave to travel the short distance through the balls is too small for human perception. Neither the momentum nor energy is perfect in efficiency. Energy is lost in the suspending wires, friction of the surrounding air, and sound (the clicking of balls). The momentum degrades with each swing until near the end of oscillation the intermediate balls are swaying.
We have had customers ask why the balls don't clack back and forth forever in perpetual motion. It's because of the energy loss with each impact. Since energy cannot be created or destroyed, there can never be a "net gain" of energy and therefore there cannot ever be a true "perpetual motion" device (note to self, make a perpetual motion device, sell it to the highest bidder, retire).
The largest Newton's Cradle is over 20 feet tall. It was designed by Chris Boden and is located at The Geek Group home base in Kalamazoo, Michigan. The monster Newtonian demonstrator is made up of 7 bowling balls weighting 15 pounds each. The bowling balls are attached to metal cables and hung from trusses in the ceiling of a warehouse. The suspension cables are 20 feet long and the bowling balls hang 3 feet from the floor.
Why a Newton's Cradle?
Because they're fascinating to watch, make a cool sound, and provide kinetic entertainment without batteries! As it turns out, this little device has become among the most classic Desk Toys of all time. We sell tons of these (literally) and take them very seriously. If you want your own steel balls transferring energy at 4699 m/s, click here to see our selection.
