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Physical Pendulum

A rigid rod executes simple harmonic motion about an adjustable pivot point.

What It Shows

The period of a physical pendulum is measured and compared to theory. The pivot point, and thus the period, is adjustable along the length of the pendulum making it possible to demonstrate that there is a pivot point where the period is a minimum (stationary point).

How It Works

The physical pendulum is a 1/2" diameter × 100cm long brass rod. A collar with a "knife edge" can be fixed anywhere along the length of the pendulum and serves as the pivot point. The period...

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Simple Harmonic Motion Demonstrator

Relation between circular motion and linear displacement on overhead projector.

What It Shows

Uniform circular motion can be shown to be the superposition of simple harmonic motions in two mutually perpendicular directions. This apparatus gives the audience a visual display of how one dimensional simple harmonic motion varies in unison with circular motion.

...

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Pascal's Paradox

What it shows:

Three containers are filled with water to the same depth, and each has the same base surface area (see figure 1). Since the pressure and area are the same in each container, the force should be the same (pressure = force/area). pascalSo how come the scales...

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Golf Ball Atmosphere

A model of molecular motion and pressure using practice golf balls.

What it shows:

The kinetic energy of gas molecules bouncing off a surface causes pressure.

Increasing the molecules' speeds increases the pressure and the volume of the gas.

 

How it works:

Plastic practice golf balls represent...

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Spiral Fracture

What it shows:

A spiral fracture is incurred when a torque is directed along the axis of a limb or shaft. Planes perpendicular to the axis are unaffected, but those parallel are twisted, which causes pure tensile forces in one part of the limb, pure compressive forces in another. Fracture occurs when either the compressive or tensile limit of the material is exceeded. This demo shows a spiral fracture in a simulated skiing accident.

How it works:

An old ski boot has a wooden plug placed snugly inside it acting as a foot. A 3 × 4cm square hole accommodates a 0.5m...

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Yo-yo

A very large cable spool (or smaller version) is made to roll in either direction or slide, depending on the angle of pull; action of a torque.

What it shows:

Depending upon the angle of applied force, a yo-yo can be made to roll forwards, backwards or simply slide without rotating.

How it works:

The effect of force angle is illustrated in figure 1; (a) and (b) are the extreme cases. For (a), pulling the string vertically creates a torque r1F rotating the yo-yo counter-clockwise. Pulling the string horizontally as in (b) creates a...

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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:...

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Hula Hoop Rotational Inertia

What it shows:

A suspended hula hoop has the same period of oscillation as a pendulum whose length is equal to the diameter of the hoop.

How it works:

The parallel-axis theorem allows us to readily deduce the rotational inertia of a hoop about an axis that passes through its circumference and is given by

I = Icm+MR2 = 2MR2

where M is the mass of the hoop and R is its radius. The period of oscillation thus becomes T = 2∏√(I/mgd) = 2∏√(2R/g), which is equal to that of a pendulum whose length...

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Tail Wags Dog

Lecturer tries to swing baseball bat while standing on turntable.

turntable

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