3A10 - Pendula

Simple Pendulum (3A10.10) A single simple pendulum with a length of 1 meter.

Simple Pendulums of Various Lengths and Masses (3A10.14) Simple pendulums with differing lengths (1 m or 0.25 m) and/or differing masses (wood or metal). For comparing the mass and length to the period.

Metronome as a Pendulum (3A10.21) A metronome is used as an adjustable pendulum.

Torsion Pendulum (3A10.30) A heavy disc at the end of a limber vertical rod can be set into torsional oscillation. Mass can be added to the disc to show the effect on the period of oscillation.

Variable Angle (Variable g) Pendulum (3A10.40) A physical pendulum is mounted on a bearing so the angle of the plane of oscillation can be changed.

3A15 - Physical Pendula

Physical Pendulum (3A15.20) Compare the period of a bar supported at the end with a simple pendulum that is 2/3 the length of the bar.

Hoops and Arcs (3A15.40) A full circular hoop and portions of a hoop of the same diameter pivot from a hole at the center of the periphery of each. Though they vary greatly in size, each will swing on the pivot with the same frequency of oscillation.

3A20 - Springs and Oscillators

Water in U-Tube (3A20.55) Colored water oscillates between two legs of a glass U-tube. Motion can be frozen at any point by corking one leg of the tube.

3A40 - Simple Harmonic Motion

Circular vs. Simple Harmonic Motion (Spring) (3A40.10) The shadow of a pin moving uniformly around a circle in the vertical plane is superimposed over that of an oscillating spring and weight. The shadows of the pin and the weight are synchronized so that the shadows move in unison on the screen.

3A50 - Damped Oscillators

Water Damped Spring and Weight (3A50.10) A weight on the end of a hand held spring is set oscillating in a water column and quickly damps out.

3A60 - Driven Mechanical Resonance

Resonant Driven Pendula (3A60.31) Three simple pendula of different lengths are hung from a horizontal bar with an attached driver pendulum. The driver pendulum is a stiff rod with an adjustable bob so that its frequency can be changed. The driver pendulum is set to the natural frequency of each pendulum in turn, and only that one pendulum oscillates.

Driven Spring and Weight (3A60.43) A mass on a spring is driven at an adjustable frequency. Damping the motion in a cylinder of water shows a small shift in the resonant frequency of the oscillator.

Driven Spring and Weight with Display (3A60.43) A newer version of the above demo (Driven Spring and Weight) but also has a marker for increased visibility.

Reed Tachometer (3A60.50) A set of metal reeds of descending natural frequencies is attached to a gyroscope. The gyroscope is slightly off balance so that it vibrates as it spins, and as its rotational frequency passes through the frequencies of the reeds each reed vibrates in turn.

3A70 - Coupled Oscillations

Spontaneous Synchronization in Metronomes (3A70.23) Five small metronomes on a lightweight board are set to the same frequency and started oscillating out of phase. At first the board sits on the table and the metronomes will oscillate independently. The board is then placed on two empty aluminum cans (on their sides) to provide some light coupling between the metronomes. The metronomes will phase lock with each other within a minute or two and their 'tick-tocks' will all be in unison.

Coupled Pendula (3A70.25) Two identical massive bobs at the ends of two pendulum rods are coupled by a spring and set swinging. Alternately each one stops oscillating as its energy is transferred to the other, then begins swinging again as the energy is transferred back. Different springs change the amount of coupling and the time required for total energy transfer.

3A75 - Normal Modes

3A80 - Lissajous Figures

3A95 - Non-Linear Systems

3B10 - Transverse Pulses and Waves

Transverse Waves (Bell Labs Wave Machine) (3B10.30) Rods are arranged like ribs along a square wire "spine." A torsional wave can be sent down the spine by sharply displacing the tip of the first rod. As the wave propagates along the spine, each rod is tipped in turn by the passage of the wave, and the displacement of the ends of the rods is visible to the class, appearing as a transverse wave (visibility can be increased by illuminating the fluorescent tips of the rods with UV).

3B20 - Longitudinal Pulses and Waves

Longitudinal Waves (Hanging Slinky) (3B20.10) Longitudinal waves propagate slowly on a large plastic slinky suspended horizontally. The slinky is hand driven and can be used to show single pulses or standing waves. Paper markers hang on the coils to increase visibility of compression and rarefaction. The far end can be free or fixed. Note: This is on the same setup as Transverse Waves (Bell Labs Wave Machine) (3B10.30).

Pasco Longitudinal Wave Model (3B20.30) The Pasco Longitudinal Wave Model is a series of vertical rods, the pivot at their centers, and are connected by springs.

3B22 - Standing Waves

Standing Transverse Waves (Driven Waves in Rubber Tubing) (3B22.10) A long piece of rubber tubing is stretched out horizontally and run over a pulley at one end, then tensioned with a hanging weight. At the other end a revolving bar strikes the tubing at a frequency which can be adjusted with a motor speed controller. Transverse waves of various frequency can thus be sent along the tubing, and when the right frequencies are reached the tubing vibrates in various standing wave modes. 1 kg and 0.25 kg masses can be used to vary the tension.

3B25 - Impedance and Dispersion

Bell Labs Machine - Impedance Matching (3B25.10) The long and short rod sections of the wave machine can either be connected abruptly (unmatched coupling) or with a section of gradually lengthening rods (matched coupling).

Bell Labs Wave Machine - Reflection (3B25.20) The Bell Labs Wave Machine with the end fixed, damped, or free to show the affect on the reflected wave.

Acoustic Coupling with a Speaker (3B25.35) A small speaker has a coupling horn which may be removed. With the horn on, the sound is much louder than with the horn off.

3B27 - Compound Waves

3B30 - Wave Properties of Sound

Phonodeik Status: Unavailable Shows the deflection of a light beam which is reflected from a delicate mirror on the diaphragm of a mechanical microphone during oscillation. An "oscilloscope" from the pre-electronic era of candle flames, levers, and ingenuity. Note: For show and tell only right now.

Light and Siren in Vacuum (3B30.3) A buzzer and a LED are mounted inside a bell jar. The air is then evacuated from the jar, and although the LED can still be seen, no sound can be heard from the siren. Also listed as 6A02.10.

3B40 - Doppler Effect

Doppler Effect (3B40.10) The pitch from a siren rises and falls as it is swung around overhead.

Doppler Reed (3B40.25) A reed mounted on the end of a rotating arm produces a tone whose pitch wobbles up and down as the arm rotates.

3B50 - Interference and Diffraction

Moire Pattern (3B50.40) Two identical patterns of concentric circles are superimposed on an overhead projector or under the document camera. The separation between their centers changes by sliding one across the other and prodcues interference patterns.

3B55 - Interference and Diffraction of Sound

Two Speaker Interference (3B55.10) Two speakers driven from a common source are mounted at the ends of a long horizontal bar. The bar can be rotated to sweep the nodes and antinodes through the class.

3B60 - Beats

Beats from Tuning Forks (3B60.11) Two matched tuning forks are used, one of which has an adjustable weight on one tine. By adjusting the weight, the forks can be set to either equal frequencies or slightly different frequencies to produce beats.

Beats from Organ Pipes (3B60.13) Two large metal pipes mounted vertically on the lecture table will resonate at low frequencies when a source of "white noise" (a Fisher burner) is placed at the bottom end. If both pipes are excited they will produce beats.

Beats from Singing Glass Tubes (3B60.16) Two small glass Rijke tubes (3D30.70) have electrically heated wire grids and moveable tubes. Move a tube so that the grid is at the 1/4 point and the tube will "sing." Put it anywhere else, and it won’t. Since the tubes are slightly different lengths, running them both together produces beats.

Beats from Two Speakers Two speakers with separate audio oscillators produce beats.

3B70 - Coupled Resonators

3C10 - The Ear

3C20 - Pitch

Siren Disc (3C20.30) A disc with eight rings of uniformly spaced holes and a ninth ring of randomly spaced holes. The disc is spun by a motor and an air jet is directed at the holes. Puffs of air through the disc as a hole passes the air jet produce pressure variations, and thus sound. Different musical notes are heard from different rings of regularly spaced holes but noise is heard from the ring of randomly spaced holes.

3C30 - Intensity and Attenuation

Decibel Meter (3C30.22) A sound level meter with output measured in decibels. Try it with your voice, a buzzer, or various instruments. Used under the document camera.

3C50 - Wave Analysis and Synthesis

Pasco Fourier Synthesizer (3C50.10) The Pasco Fourier Synthesizer is connected to a speaker and an oscilloscope. The synthesizer can generate two fundamentals of 440 Hz and eight higher harmonics, each with amplitude and phase control. The synthesizer can produce either sine, square or triangular wave forms. Note: While it works fine, there are several nice java applets available.

3C55 - Music Perception and the Voice

3D20 - Resonance in Strings

Sonometer (3D20.10) The ends of a stretched steel wire are hooked to an audio amplifier and a small horseshoe magnet is placed over the wire, so that transverse vibrations of the wire are transformed into currents along the wire. The currents are amplified and fed into an oscilloscope to display the waveform. The wire is finger plucked, and both tension and length are adjustable. Harmonics can be either ignored or intensified by changing placement of the magnet, and can also be damped out selectively with a small brush.

3D22 - Stringed Instruments

3D30 - Resonance Cavities

Vertical Resonance Tube (256/512 Hz) (3D30.10) A glass cylinder is filled with water to one of two preset levels and the tuning fork with a frequency equal to the resonant frequency for that level is held over the opening. It is noted that the sound is much louder than when the tube is filled to any other level.

Open and Closed Resonance Tube (256/512 Hz) (3D30.20) A metal tube is cut to length to resonate at 256 Hz when closed and 512 Hz when open.

Helmholtz Resonators (3D30.40) Spherical cavities can be made to resonate loudly by a tuning fork of the corresponding frequency.

3D32 - Air Column Instruments

Open and Closed End Pipes (3D32.25) A variety of organ pipes with different lengths and removeable end pieces to show the effects of pipe length and the difference between open and closed end resonators.

3D40 - Resonance in Plates, Bars, Solids

Xylophones Wood or metal xylophones covering an octave or two.

Rectangular Bar Oscillations (3D40.11) A long metal bar with a rectangular cross section. A high pitch longitudinal oscillation is excited by hammering the end. Two lower transverse frequencies are excited by striking one side or the other of the bar, with the wider side having the lower frequency.

Water Spouting Bowl (3D40.51) A 15" diameter decorative bowl with handles is partially filled with water. Wet your hands and then rub the handles to create resonance. The standing wave will cause the water to jump up several inches or more.

3D46 - Tuning Forks

Tuning Forks (3D46.15) Various tuning forks for show and tell.

3E20 - Loudspeakers