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Chaotic Pendulum

Coupled, double, physical pendulum executes chaotic motion when non-linear initial conditions are imposed.

What it shows:

A double pendulum executes simple harmonic motion (two normal modes) when displacements from equilibrium are small. However, when large displacements are imposed, the non-linear system becomes dramatically chaotic in its motion and demonstrates that deterministic systems are not necessarily predictable.

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Musical Bottle

A beer bottle becomes a Helmholtz resonator when air is blown across its mouth.

musical bottle

Eddy Current Damping

What it shows:

A sheet of aluminum falls slowly between the poles of a magnet because induced currents in the sheet set up magnetic fields which oppose the motion.

How it works:

As the aluminum sheet falls between the poles of the magnet, eddy currents are induced in the metal. These currents set up their own magnetic fields, which through Lenz's law oppose the change that caused them. As the cause is gravity pulling the sheet to Earth, the sheet decelerates as it passes between the poles of the magnet, only to accelerate again...

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Malus' Law

What it shows:

Polaroid filters absorb one component of polarization while transmitting the perpendicular components. The intensity of transmitted light depends on the relative orientation between the polarization direction of the incoming light and the polarization axis of the filter and is described quantitatively by Malus' cos2θ intensity law.

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Saddle Shape Universe

Curved space segment for open universe geometry.

What it shows:

Whether the Universe continues to expand forever or will collapse back in upon itself depends upon the amount of matter it contains. For a density parameter Ω less than unity the Universe will not have enough mass to collapse and will be in a state of perpetual expansion. In general relativity, the curvature of space is dependent upon the density of the Universe, and for Ω<1 the curvature is negative or hyperbolic. It can be represented two dimensionally (see Comments) by a saddle...

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Eudoxos Hipoped Machine

Electrically driven machine to represent retrograde planetary motion according to Aristotle's theory of concentric spheres.

What it shows:

This is the realization of a proposed solution to retrograde motion put forward by Eudoxus (427 - 347 B.C.). Here a combination of three uniform circular motions produces retrograde motion.

How it works:

The hippopede machine consists of three concentric rings, with a point on the innermost representing the position of the planet. The assembly in figure 1 is held vertically in...

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Hydrogen Peroxide Decomposition by Iodide

Hydrogen peroxide 30% in a large round flask decomposes to boiling water and oxygen when postassium iodide is added.

The 12L Round Bottom Flask is set on white C-Fold towels covering a large cork ring on the lab bench.  100-150 ml of 30% hydrogen peroxide is carefully poured in. The liquid should be visible against the white towels from the perspective of the class, and any camera, if used.

The catalyst is 5 g of potassium iodide in a small plastic weighing boat labeled KI.

Safety goggles and gloves. Raise the projection screen and make sure the flask is...

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Buoyant Force Measurement

What it shows

We have three 20 oz. soda bottles, one filled with water, one filled with sand, and one filled with air. A spring scale shows the water-filled bottle to weigh approximately 6N in air, and nearly 0N when it is fully submerged in a large container of water. Since gravity is still acting on the bottle when it is submerged in the water, there must be a force of 6N pushing up on it. This is the buoyant force.

We can do the same experiment with the bottle of sand. This bottle weighs roughly 13N in air, but when it is fully submerged in water it weighs 6N less. Even...

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Vector Sum of Forces

Magnetic blackboard mechanics with spring balances and weights.

What it shows:

Solve a problem in composition of concurrent forces by graphical or trigonometric means.

How it works:

The blackboard mechanics set1 includes apparatus to demonstrate most of the common laws of statics and some dynamics. The pieces of apparatus are held on the blackboard by magnets and, although not large, are fairly visible in the lecture hall. A booklet with a few dozen suggested demonstration experiments is included in the set.
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