Plastic Wiffle Ball with built-in shriek to throw past (or at) your audience.
What it shows:
Waves emitted from a moving source are Doppler shifted to higher frequencies when moving toward the observer, and shifted to lower frequencies when moving away. This audio demonstration is also a useful analog to the optical red shift and blue shift exhibited by astronomical sources moving relative to the Earth.
How it works:
A plastic Wiffle-Ball™ is filled with foam padding to protect an enclosed mini-speaker 1 and its...
Smoke cell under microscope; smoke particles seen bombarded by air molecules.
What it Shows
Brownian motion shows direct evidence of the incessant motion of matter due to thermal energy. Here we use the random bombardment of smoke particles by air molecules.
How it Works
The CENCO Brownian Movement Apparatus consists of a metal chamber with a glass viewing window on top and a lens on one side (see figure 1). Smoke from a piece of smoldering rope or match is drawn into the chamber through an inlet tube by squeezing the rubber bulb....
Vinegar and two different amounts of baking soda in plastic soda bottles with balloons.
Two 500ml PETN soda bottles of the same make, split a bottle of vinegar between them.
11" balloons are pre-inflated with dry air, with care taken not to stretch the neck of the balloon. Into the balloons with a funnel go one, two teaspoons of baking soday. With 250 ml of vinegar, that's like six liters of gas potential if one carbon dioxide comes from one acid hydrogen ion.
Tap the baking soda powder down away from the neck of the balloon. Stretch the neck and place it over the top...
Bell plates are polygonal-shaped flat pieces of sheet metal which, when held in the hand and struck with a beater, produce a pleasant, sustained, slightly bell-like tone. Compare this to any arbitrary shaped piece of metal which produces a "clunk" when struck. The sound of the bell plate depends strongly on its shape and even the most modest change in the symmetry (like snipping off a corner) or proportions will make it go clunk when struck.