[★★★]

Loop-the-loop

A toy car rolling down a loop-the-loop track demonstrates the minimum height it must start at to successfully negotiate the loop.

What it shows:

For an object to move in a vertical circle, its velocity must exceed a critical value vc=(Rg)1/2, where R is the radius of the circle and g the acceleration due to gravity. This ensures that, at the top of the loop, the centripetal force balances the body's weight. This can be shown using a toy car on a looped track.

How it works:

The car is released from the top of a ramp and runs down a slope towards...

Read more about Loop-the-loop
Circular Motion and Simple Harmonic Motion

Simultaneous shadow projection of circular motion and bouncing weight on spring.

What It Shows

One of the simplest of periodic motions is uniform circular motion. By shadow projecting both uniform circular motion and oscillatory simple harmonic motion onto a screen, one can show that these two seemingly different kinds of motion are actually identical.

How It Works

A 8 cm diameter plastic ball mounted near the edge of a 46 cm diameter disk undergoes uniform circular motion. The disk, oriented vertically, is driven by a 57 RPM motor.1 A large...

Read more about Circular Motion and Simple Harmonic Motion
Hand Cranked AC Generator

Observe the induced current in a gimbaled coil as it rotates in Earth's magnetic field.

What it Shows

A changing magnetic flux through a circular coil of wire induces a current in the wire. By spinning a circular coil of wire at constant frequency and measuring the induced voltage across its ends we can find the local direction and magnitude of the Earth's magnetic field as it passes through the coil. The commutators of the coil are configured to produce an alternating current.

...

Read more about Hand Cranked AC Generator
Syrup Tube

What it shows:

Linearly polarized light, propagating down a long glass tube filled with corn syrup, is made to rotate its direction of polarization by the optically active corn syrup. The intensity of the 90° scattered light varies dramatically, in a periodic manner, along the length of the tube -- the intensity being zero when the dipole radiators oscillate in the line of sight direction, and maximum intensity when they oscillate perpendicular to the line of sight. Scattered light is most intense when the electric field vector is perpendicular to the line of sight.

...

Read more about Syrup Tube
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...

Read more about Radioactive Human Body
Giant Vibrating Crystal

What it shows:

A simplified model crystal with non-rigid inter-atomic bonds. You can show that solids really do vibrate, distort and expand.

How it works:

A cubic lattice of 3×3×3 15cm diameter Styrofoam™ spheres linked by 3cm steel springs. The springs are epoxied to corks embedded in the Styrofoam.

...

Read more about Giant Vibrating Crystal
Specific Heat of Air and Water

Two clean plastic cups, one filled with room temperature water, the other empty, for a student to test with their finger.

Supported by experience, this is a way to introduce heat capacity as an important variable in measuring temperature.

Make sure the water has been in the room long enough to equilibrate. Cover the water as any evaporation will cool it.

Food safe cups and potable water. And safety glasses, because why not?

Buoyant Force on Finger

What it shows

An object does not need to float in order to experience the buoyant force.

finger about to push against liquid in a cup

In this example we see a cup of water at rest on a pan balance. When the demonstrator pushes a finger down into the liquid, the buoyant force of the liquid pushes...

Read more about Buoyant Force on Finger

Pages