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 Oscillations and Waves View Printable Version

## 3A - Oscillations

### 10. Pendula

3A10.1 Simple Pendulum
A mass at the end of a string. (For dramatic effect, one could use the 50 lbs. pendulum of 1M40.1)
[Set-Up Time: 5 min.]
[Current Condition: Good]

### 20. Springs and Oscillators

3A20.1 Mass on a Spring
A mass oscillates on a spring. A variety of springs and a set of different weights can also be provided.
[Set-Up Time: 5 min.]
[Current Condition: Good]

Single Spring and Mass: Assorted Springs and Masses:

3A20.2 Four Vibrating Masses
Show that the frequency depends on (k/m)^1/2. Four masses are held on separate flexible metal strips. The masses are: 1m, 1m, 4m, 4m; the strips are 1 k, 4k, 1 k, 4k. The first and last oscillators move at the same rate; the second one twice as fast, the third one twice as slow.
[Set-Up Time: 1 min.]
[Current Condition: Good]

### 40. Simple Harmonic Motion

3A40.1 Circular Motion vs. Mass on a Spring
A mass moves up and down on a spring; a peg moves up and down on a rotating circle; a light source projects their shadows onto a screen, and the superimposed images move in synchronized motion.
[Set-Up Time: 15 min.]
[Current Condition: Good]

Front View: Side View:

3A40.52 Simple Harmonic Motion with a Pasco Motion Sensor
A Pasco motion sensor is used to record the motion of a mass oscillating on a spring or a pendulum. The output of the motion sensor is viewed in graphs of displacement, velocity and acceleration versus time on the computer; the image on the computer monitor can be projected onto a screen. The demonstration clearly shows the phase relationships between the position, velocity and acceleration and the effects of damping, if the oscillation is allowed to run for a minute or so.
[Current Condition: OK- Pasco software only installed on one laptop- need advanced warning for requesting]

### 60. Driven Mechanical Resonance

3A60.1 Tacoma Narrows Bridge Collapse - Video
Five to ten minutes of video showing the bridge before, during and after its collapse. From the Mechanical Universe series.
[Current Condition: Good]
make sure to load the video beforehand
additionally, here is a color version of a more recent bridge in Russia:
and a small wooden suspension bridge's various modes:
[Set-Up Time: 10 min.]

3A60.2 Forced Mechanical Oscillator
THE OLD VERSION SEEN HERE IS BROKEN:
Side View: Front View: Back View:

The new version is bascially good to go, but it has some chaotic behaviors at around half speed (slow and fast work well though):

The frequency of a driving force on a spring can be varied to above, below, and (watch out!) at resonance. A mass hangs at the bottom of the spring, and it can be suspended in water to show the effect of damping.
[Set-Up Time: 15 min.]
[Current Condition: OK]

### 70. Coupled Oscillators

3A70.1 Spring-Coupled Pendula
Two physical pendula are connected horizontally by a spring. Pull one pendulum back while holding the second one at equilibrium. Release, and the oscillation gradually transfers from the first pendulum to the second. Varying the height of the spring changes the period of the transfer.
[Set-Up Time: 15 min.]
[Current Condition: Good]

3A70.10 Wilberforce pendulum
A mass with a large torsional moment hangs from a spring. Energy is transferred between vertical and torsional modes.
[Setup time: 2 min.]
[Current Condition: Good]

### 75. Normal Modes

3A75.1 Spring-Coupled Pendula
Same as 3A70.1 above. This time, however, observe the two normal modes by a) releasing both pendula from the same side or b) releasing them from opposite sides.
[Set-Up Time: 15 min.]
[Current Condition: Good]

3A75.10 Coupled harmonic oscillators (Normal modes)
Two or three riders on the air track are connected with springs to each other and to the air track frame. Normal modes can be excited by hand.
[Setup time: 15 mins.]
[Current Condition: Good]

### 80. Lissajous Figures

3A80.1 Lissajous Figures on the Oscilloscope
Two function generators at different frequencies drive the horizontal and vertical inputs of an oscilloscope, projected on a TV screen.
[Set-Up Time: 20 min.]
[Current Condition: Good]

### 95. Nonlinear Systems

3A95.45 Jump phenomena
A rider on the air track is driven sinusoidally but the restoring force (rubber bands) does not quite obey Hooke's law. This yields Duffing's equation rather than the familiar linear oscillator equation. The system exhibits jumps between high and low amplitude when crossing over the resonance.
[Setup time: 25 mins.]
[Current Condition: Good]

3A95.50 Double Pendula
Two double pendula are set up on a stand. No matter how close the initial conditions, their behavior will always diverge. The pendula keep swinging for several minutes.
[Setup time: 5 mins.]
[Current Condition: Good]

3A95.60 Parametric resonance of a pendulum
The pivot of a pendulum is driven vertically at a variable rate. Driving at twice the pendulum's natural frequency excites the system into resonance.
[Setup time: 20 mins.]
[Current Condition: unavailable, updating]

## 3B - Wave Motion

### 10. Transverse Pulses and Waves

3B10.1 Long Spring
Stretch a long spring across the front table. Give the spring a small pluck at one end and watch the pulse propagate down and back. Can show the dependence of wave velocity on tension by stretching the spring more or less.
[Set-Up Time: 2 min.]
[Current Condition: Good]

3B10.2 Torsion Wave Machine (also called Shive or Bell Labs Wave Machine)
A long array of horizontal metal bars are fixed on a central wire. Pulling up on one of the bars at one end twists the spine and send a smooth wave down to the other end and back. Also shows standing waves (see Standing Waves 3B22.2).
[Set-Up Time: 5min.]
[Current Condition: Good]

### 20. Longitudinal Pulses and Waves

A long slinky is stretched across the table; compressing it suddenly sends a longitudinal pulse along it.
[Set-Up Time: none]
[Current Condition: Good]

### 22. Standing Waves

3B22.1 Standing Waves on a String (formerly Modes of Vibration)
A long string is stretched across the full length of the front table; at one end it goes over a pulley to a mass hanging over the edge, at the other end it is driven by a mechanical oscillator. Vary the frequency of the oscillator using a function generator to show standing waves of different harmonics. The tension in the string can also be changed by adjusting the mass at the end of the string.
[Set-Up Time: 15 min.]
Images available soon.
[Current Condition: Good, need advance warning to hunt down a strobe light]

3B22.2 Standing waves on the Torsion Wave Machine
Same apparatus as 3B10.2. Moving one end gently by hand, it is easy to set up a standing wave.
[Set-Up Time: 5 min.]
[Current Condition: Good]

3B27.20 Columbia Wave Machine (Adding Waves Apparatus)
As a crank is turned, three sets of dots oscillate to show three types of wave motion: transverse, longitudinal, and composite (transverse + longitudinal, or "ocean" waves). This machine is an antique. The transverse dots are labeled "Ether Waves" - the patent for this apparatus was filed in 1905.
[Set-Up Time: 5 min.]
[Current Condition: OK, parts are broken/not functioning]

### 30. Wave Properties of Sound

3B30.1 Sound in Vacuum
A speaker ringing alarm driven with a sine-wave generator is suspended inside a bell jar. The sound fades away as the air is pumped out and returns when vented. The generator can be set to sweep over frequencies, giving a siren-like sound that is unmistakable over the sound of the vacuum pump. A piece of foam can also be placed on the speaker cone; it bounces to show the speaker is still moving even though no sound is heard.
[Set-Up Time: 5 min.]
[Current Condition: OK- still some buzzing from vibration]

### 40. Doppler Effect

3B40.1 Doppler Whistle
Air is blown out the end of a long rotating pipe. As the speed increases, the pitch of the whistling rises and falls more dramatically.
[Set-Up Time: 20 min.]
[Current Condition: Good]

### 50. Interference and Diffraction

3B50.1 Ripple Tank
A mechanical driver with two knobs sends ripples through water in shallow tank, and an overhead projector projects this image onto the screen. The relative phase and the frequency of the two knobs can be varied; in addition there is an assortment of one slit and two slit apertures as well as concave and convex reflectors that can be placed in the water.

[Current Condition: Good]

Image Projected on Wall:

3B50.22 Double Source Sound Interference
Two identical speakers are connected to an amplifier and a function generator. As students move around the room they clearly hear loud and soft spots as they walk along a row or move up and down. Measurements of distance can be made to determine the speed of sound.
[Note: This has only been tested in Rooms 428 and 329; it should also work in 301].
[Set-Up Time: 25 min]
[Current Condition: Good]

3B50.40 Moire Transparencies
Transparencies with a circular wave pattern can be overlayed to show interference patterns.
[Setup time: 2 mins.]
[Current Condition: Good]

3B50.52 Superposition Computer Simulation
This simulation program shows two differently colored waves approaching each other and the resulting superposition in a third color. Parameters which can be altered for each wave include wavelength, velocity, and amplitude. The image from the computer is displayed onto a TV screen.
[Set-Up Time: 15 min]
[Current Condition: Unknown]

### 60. Beats

3B60.1 Beats with Tuning Forks
Two 256 Hz tuning forks are struck and shown to have the same pitch. Then a bit of clay is stuck to the side of one of the forks. Struck by itself, the difference is barely detectable, but a beat is heard if both forks are struck at the same time.
[Set-Up Time: 2 min.]
[Current Condition: Good]

3B60.18 Beats with Function Generators
Two speakers are connected to different function generators. Beats can clearly be heard when the frequencies are nearly identical.
[Set-Up Time: 10 min]
[Current Condition: Good]

Setup (except for additional function generator required):

3B60.21 Beats Computer Simulation
Show beats using the program described in 3B50.52.
[Set-Up Time: 15 min.]
[Current Condition: Unknown]

### 70. Coupled Resonators

3B70.1 Sympathetic Vibration in Tuning Forks
Two 256 Hz tuning forks are placed opposite each other. When one is struck, then stopped, the other can be heard (faintly - not ideal for a large lecture class!).
[Set-Up Time: 2 min.]
[Current Condition: Good]

## 3C - Acoustics

### 20. Pitch

3C20.1 Range of Hearing (or Limit of Audibility)
A series of metal bars with increasing frequencies up to 30 kHz. Strike them in order and discover that the students can hear more of them than you can. A similar effect can be accomplished using a function generator and varying the frequency from 10 kHz to 20 kHz. An oscilliscope can also be set up to display visual confirmation
[Set-Up Time: 2 min.]
[Current Condition: Good]

### 50. Wave Analysis and Synthesis

3C50.1 Fourier Synthesis
A Fourier synthesizer connects to a speaker and oscilloscope, projected on TV screen. The synthesizer allows one to construct an arbitrary waveform by setting the amplitude and phase of a tone and its first nine harmonics.
[Set-Up Time: 30 min.]
[Current Condition: Good]

3C50.13 Fourier Analysis of Sound
A sonometer computer program breaks up a sound (instrument, voice, tuning fork, etc.) into its Fourier components. The program shows the frequency of the harmonics on the y-axis as time scrolls through on the x-axis. The amplitude is displayed at the top of the screen in a graph showing the loudness of the sound on the y-axis as time scrolls through on the x-axis. The image from the computer is displayed onto a TV screen.
[Set-up Time: 20 min]
[Current Condition: unknown- in principle I could try and set up something with an oscilliscope that does FFT's, but please give advanced warning if you'd like me to try]

## 3D - Instruments

### 30. Resonance Cavities

3D30.52 Resonance Fountain Tube
A horizontal meter-long tube filled with kerosene is driven by a speaker. At resonant frequencies the standing waves produce visible depressions at the antinodes, and large, erupting fountains at the nodes. The speaker is very loud upwards of 150 Hz.
[Set-Up Time: 15 Min.]
[Current Condition: Good]

Also newly available:
Rueben's tube, which does the same thing but with flame jets.

### 32. Air Column Instruments

3D32.1 Pipe Organ
A small wooden organ with a keyboard and interchangeable pipes can be connected to an external air supply.
[Set-Up Time: Unknown]
[Current Condition: unknown]

### 40. Resonance in Plates, Bars, and Solids

3D40.1 Musical Sticks
A set of wooden sticks will play a major scale when dropped on the table.
[Set-Up Time: 2 min.]
[Current Condition: good]