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Reactionary Roadbed

Radio controlled car moves one way while road moves the other.

What it shows:

We tell our students that, when a car drives down the road, the road and the Earth move in the opposite direction, albeit imperceptibly. This demonstration is a realization of that concept, made possible (and perceptible) by the fact that the road is not attached to the Earth.

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Golf Ball Atmosphere

A model of molecular motion and pressure using practice golf balls.

What it shows:

The kinetic energy of gas molecules bouncing off a surface causes pressure.

Increasing the molecules' speeds increases the pressure and the volume of the gas.

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Walk-In Faraday Cage

What it shows:

A lecturer's faith in the principle that an electric field cannot exist inside a charged conductor is put to the test using a Faraday cage that is large enough to sit in.

How it works:

The lecturer (or some volunteer) climbs the three steps and sits upon a plain wooden chair. Their assistant pulls the mesh door closed and fastens it. A Van de Graaff, whose dome is in contact with the cage, begins to charge itself and the cage up to a high voltage. The person inside is oblivious to the large amount of charge now...

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Radioactive Human Body

What it shows:

Gamma ray spectroscopy is used to detect the minute amount of radioactive potassium-40 present in the human body. Using a NaI(Tl) scintillation detector in conjunction with a multichannel pulse-height analyzer (PHA), 1.46 MeV gammas originating from the human body are detected. The source of these gammas is K-40 which has a half-life of 1.26 billion years, and is the main source of radioactivity inside the body. The second most active radionuclide in the body, carbon-14 (5,730 yr half-life), can not be detected with this apparatus because it is a...

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Vortex Shedding in Air

A thin wire, moving through the air, is made to vibrate in the audio range at the vortex shedding frequency.

What it Shows

When air flows around an object, there is a range of flow velocities for which a von Karman vortex street is formed. The shedding of these vortices imparts a periodic force on the object. The force is quite small and not enough to accelerate the object to any significant amount, especially if the object is relatively massive. If the situation is such that the object can vibrate about a fixed position, we have the possibility of simple...

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Rocket Car

Single seat CO2 powered rocket cars.

rocket car
Photo by Rose Lincoln

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