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Foucault Pendulum Model

What it shows:

A "working model" of a Foucault pendulum to show how its oscillations appear to change due to the rotation of "Earth" below it.

How it works:

The pendulum consists of 9-cm diameter brass ball suspended from a sturdy tripod which, in turn, sits on a heavy 3-ft diameter wooden disk. The disk represents the Earth with a projection of the northern hemisphere drawn on it. The suspension point of the pendulum is positioned over the North Pole. The entire apparatus sits on a ring bearing and the disk (Earth) can be rotated slowly by hand. While the plane of...

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Uncertainty Principle

What it shows:

A pulse-modulated electromagnetic signal is simultaneously displayed in the time domain (on an oscilloscope) and in the frequency domain (on a spectrum analyzer). Using ∆n for the frequency spread (uncertainty in frequency) and ∆t for the duration of the pulse (uncertainty in the time domain), the frequency-time uncertainty relation is given by 1

∆n ∆t ≥ 1/

By progressively shortening the length of time that the carrier signal is on, the inverse relation between pulse length and spectral-energy...

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Mercator Projection

What It Shows

As shown in the drawing, the Mercator projection is a cylindrical map projection of the spherical globe. The meridians and parallels of latitude on the globe end up appearing as lines crossing at right angles in the projection. Areas on the globe far from the equator appear to be much larger on the projection. It's not trivial to visualize this projection and the intention of this demonstration is to shed some light on it (literally).

...

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Foucault Pendulum

Plane of pendulum oscillation appears to change due to rotation of Earth.

What it shows:

Due to the rotation of the Earth, the plane of oscillation of a pendulum will rotate with respect to the surface beneath it. We expect a rotation of about 10˚/hr at our latitude of 42.˚

How it works:

Here the observer standing on the Earth resides in the reference frame, with the swinging pendulum oscillating in a rotating frame. From the pendulum's point of view, it keeps oscillating in the same plane, but the Earth spins below it. The deflection from its original plane...

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Seismic Wave Refraction

Total internal refraction of laser beam through sugar solution with refractive index gradient; representative of seismic waves through Earth's mantle.

What it shows:

As a simulation of atmospheric refraction, this demonstration shows the gradual and continuous bending of light due to a gradient in the optical density of the medium. In this case the variable refracting medium is a tank of sugar water with a vertical gradient in the concentration of sugar and a HeNe laser provides the light beam. It can be used as a model of mirage formation (except that the...

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Egg Shell Strength

What it shows:

Eggs have a reputation for being quite strong under compressional loads. You won't believe your eyes when you see how strong they actually are — an egg can support a person!

How it works:

An egg shell is a composite material, but primarily calcium carbonate, "nature's ceramic."1 We assume the ultimate compressional strength of the material to be about the same as bone (which is mostly calcium phosphate, but never mind): 170x106 N/m2. The diameter of a "large" chicken egg is about 1.75" and the typical shell...

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