CRT Paddle Wheel

A beam of cathode rays (electrons) impinging on a paddle wheel cause it to spin and travel down the vacuum tube.

crookes tubes

What it Shows

A paddle wheel is suspended by its axle inside a Crookes tube so that when the paddle vanes spin the entire wheel is free to travel the length of the tube… Read more about CRT Paddle Wheel

Critical Opalescence

What it shows:

The demonstration shows density fluctuations in liquids. These fluctuations are particularly spectacular near critical points. A binary fluid mixture of methanol (29% by weight) and cyclohexane (71%) becomes opalescent when heated up to its critical temperature (about 45˚C) ... the fluids become miscible above this temperature.

How it works:

The two fluids are sealed in a special vial, able to withstand elevated pressure. The fluids are immiscible at room temperature. When brought up to 45˚C, they become miscible… Read more about Critical Opalescence

Jupiter's Satellites

Static model of satellite orbits.

What it shows:

Static 3-D model showing the orbital paths of Jupiter's satellites.

How it works:

The model marks the orbital paths of the Jovian satellites to a scale of 1.5cm = 106 km. This scale allows the orbit of the outermost satellite Sinope to fit within a 1m × 1m plywood base. The orbits of the outer 8 satellites are marked using loops of 2mm × 1mm spring steel supported to their correct heights by 5mm Plexiglas rods (Pasiphae rising to the greatest height of 42cm). The… Read more about Jupiter's Satellites

Nitrogen Phase Change

Liquid nitrogen is pumped on and freezes into a sponge of solid nitrogen.

The liquid nitrogen is in a 600 or 800 ml beaker under a shielded bell jar on top of the red vacuum cart. A cold trap is not necessary if only nitrogen is being pumped on.

It is important that the beaker of liquid nitrogen not have frozen water vapor on its side, as the view is impaired. A camera is zoomed in on the beaker, which is in a thick glass bell jar and an acrylic tube shield.

With the pump running and the bell jar vent open, pour the nitrogen and cover the beaker with bell jar. Open up… Read more about Nitrogen Phase Change

Shoot the Monkey

Monkey released from platform is shot by simultaneously fired cannon.

What it shows:

This is a demonstration of the independence of the horizontal and vertical components of velocity of a projectile. Often referred to as "the monkey and hunter," the problem is the following. A hunter (at ground level) aims a gun at a monkey hanging from a branch high in a tree. The monkey, being very intelligent, does not want to be shot. It knows that light travels faster than bullets and reasons that, if it lets go of the branch the instant it sees the flash of the gun,… Read more about Shoot the Monkey

Reversible (Kater's) Pendulum

A physical pendulum with two adjustable knife edges for an accurate determination of "g".

What It Shows

An important application of the pendulum is the determination of the value of the acceleration due to gravity. By adding a second knife-edge pivot and two adjustable masses to the physical pendulum described in the Physical Pendulum demo, the value of g can be determined to 0.2% precision.

How It Works

Using a simple pendulum, the value of g… Read more about Reversible (Kater's) Pendulum

Tennis Racquet Flip

What it shows:

A simple and convincing demonstration of the intermediate axis theorem. Consider an object (a tennis racquet in this case) with three unequal principle moments of inertia. If the racquet is set into rotation about either the axis of greatest moment or least moment and is thereafter subject to no external torques, the resulting motion is stable. However, rotation about the axis of intermediate principle moment of inertia is unstable — the smallest perturbation grows and the rotation axis does not remain close to the initial axis of rotation.

How it works:… Read more about Tennis Racquet Flip

Capillary Action

What it shows:

capillary actionDue to surface tension effects water rises up a narrow bored tube; the rise in height being inversely proportional to the bore's radius.

How it works:

The setup shows the direct comparison between four… Read more about Capillary Action

Refraction of Sound

Balloons filled with helium, CO2, or SF6 act as diverging and converging lenses, respectively.

What it shows:

A balloon, filled with a gas different from air, will refract sound waves. A gas denser than air turns the balloon into a converging lens and a lighter gas makes it a diverging lens. An air-filled balloon has little effect.

How it works:

The refraction phenomenon occurs whenever waves travel from one medium to another in which the velocity of the wave changes. The amount of refraction at… Read more about Refraction of Sound