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Newton's Cradle

What it shows:

Demonstration of elastic collisions between metal balls to show conservation of momentum and energy.

How it works:

Newton's Cradle (less affectionately known as Newton's Balls) consists of six rigid balls hanging in a row with bifilar suspension. The balls hang so that they just barely touch their neighbor.

Various initial conditions can be employed. A single ball displaced will collide with the remaining four, sending the ball at the far end off. Same idea for two or three balls. Four balls, and only the first two will stop; the center two...

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Frahm Resonance Gyroscope

Vibrational resonances of metal reeds are excited by a spinning gyro as it slows down.

How it works

The Frahm resonance gyroscope is a standard piece of equipment that can be purchased from science supply houses. 1 It consists of a heavy wheel slightly unbalanced, held in a frame to which seven metal reeds are attached, each having a different vibrational frequency. The wheel is set in motion by unwinding a string that has been wrapped around the axle. As the wheel runs down, it sets each reed successively into vibration as its rotational frequency passes through...

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Electromagnetic Spear

What it shows:

Static 3-D stylized model of an electromagnetic wave, with two sets of sinusoidal fins at 90° representing the E and B fields.

How it works:

The wave packet model consists of a wooden spine with E and B fins of 1cm wooden dowels. A plastic arrowhead gives the spine a direction.

Figure 1. The Spear

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Sugar Syrups

What it shows:

Certain materials (sugar in this experiment) are optically active because the molecules themselves have a twist in them. When linearly polarized light passes through an optically active material, its direction of polarization is rotated. The angle of rotation depends on the thickness of the material and the wavelength of the light.

...

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Precession Globe

Globe pivoted so north pole can precess.

What it shows:

Due to the oblateness of the Earth, the gravitational force between the Earth and the Sun sets up a couple which causes the Earth's axis of rotation to precess. An adapted globe shows what is meant by precession.

How it works:

An old 8" (19cm) globe has been modified 1 to allow it to precess on its axis. A 23° cone is cut into the south pole, and a cone of metal supported by a metal equatorial ring has been inserted. This makes the globe bottom heavy (and...

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Orbiter

Ball on string orbits with increasing speed as string is shortened.

What it shows:

An object moving in a circular orbit of radius r has an angular momentum given by:

L = r × mv = mr2ω.

A simple way to show conservation of angular momentum is a ball on a string, whirled around your head. As you change the length of the string, the ball's orbital speed changes to conserve angular momentum.

How it works:

The orbiter consists of a meter length of cord with a wooden ball at one end and a wooden anchor at the other. The cord passes...

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OHP RLC Circuit

What It Shows

The current in a circuit consisting of a capacitor, inductor, and resistor will oscillate back and forth as the capacitor charges and discharges.

How It Works

The circuit layout is shown in the figure below. Initially the knife switch links the capacitor to the battery. Switching to complete the LRC circuit allows the capacitor to discharge. The current I in the circuit increases, as does the magneic field B inside the inductor. When the capacitor charge is zero, I and B are a maximum (the energy of the circuit is now stored in the inductor). As the...

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