Pendula: Oscillations
Simple Pendulum
PIRA Class: 3A10.10
Purpose
To demonstrate the simple harmonic motion of a mass on a string (suspended from a fixed pivot point).
Description
Using a "massless" string to suspend a simple steel ball, set a pendulum bob into motion.
VARIATIONS:
- Use the bowling ball pendulum in large classrooms. Student will be able to better observe the “zero” motion at the pendulum’s maximum displacements.
- To aid in the discussion of simple harmonic motion use a strong light source (slide projector without its lens?) to project the swinging bob's shadow onto the classroom board. Equilibrium, maximum, & minimum points can then be drawn on the board and the motion better studied. Note: make sure bob's motion stays on a plane parallel to the board
- Conservation of Energy Illustration: Add a "stop" (a second fixed rod) in the path of the bob's string. Challenge students to predict what will happen when the bob is released and the bob’s string comes into contact with the “stop”. They will observe that the bob will rise to the same height on the opposite side of its swing. Using shadow projection, this demo variation can be quite effective in illustrating conservation of energy.
Equipment
Pendulum Bob
Support Equipment
Ring Stand
Pendula: Oscillations
Bowling Ball Pendulum
PIRA Class: 3A10.15
Purpose
Demonstrate the simple harmonic motion of a swinging bowling ball.
Description
Suspend a bowling ball from a chain attached to the classroom ceiling; rooms 102 & 104 are equipped for this demonstration.
Equipment
Bowling Ball & Chain
Support Equipment
Stepladder & hanging rod
Pendula: Oscillations
Torsion Pendula
PIRA Class: 3A10.30
Purpose
To demonstrate torsional simple harmonic motion and to show the effect of moment of inertia on the period.
Description
Observe the period (and its dependence on moment of inertia) of a torsion pendulum hung from a wire.
Equipment
Torsional Pendula and masses
Support Equipment
Pendula Stand
Physical Pendula: Oscillations
Baseball Bat Physical Pendulum
PIRA Class: 3A15.10
Purpose
To observe motion of a distributed mass pendulum.
Description
A baseball bat is hung from a pivot rod and set into oscillatory motion.
Equipment
Baseball bat with a hole drilled through its handle.
Support Equipment
Ring Stand
Physical Pendula: Oscillations
Ring Physical Pendula
PIRA Class: 3A15.10
Purpose
To observe and compare the motion of two identical (yet with different moments of inertia) ring pendula.
Description
Two ring pendula are set into swinging motion and their motion’s frequencies are calculated and compared.
Equipment
Two large ring pendula with magnetic blackboard mounts, stopwatch
Spring & Oscillators: Oscillations
Mass on a Spring
PIRA Class: 3A20.10
Purpose
To demonstrate the simple harmonic motion of a mass on a spring.
Description
Mass, suspended from a spring, oscillates slowly up and down.
Choose a mass such that its frequency is slow enough to make basic observations, yet heavy enough to prevent motion from dampening out too quickly.
VARIATIONS:
- Hang the same mass from two springs hung parallel
- Hang the same mass from two springs hung in series
-Use PASCO's motion detector (& Science Workshop computer interface) to analysis the real-time motion of the mass. (x vs. t, v vs. t, and a vs. t).
-For large classrooms, use a mass suspended from a modified slinky hung from the classroom ceiling.
Equipment
Various springs, masses
Support Equipment
Spring stand
Spring & Oscillators: Oscillations
Air Track Glider & Spring
PIRA Class: 3A20.30
Purpose
Description
Air cart is attached to a single horizontal spring.
Equipment
Air Track & Accessories, Spring
Support Equipment
Air Supply
Spring & Oscillators: Oscillations
Air Track Glider between Springs
PIRA Class: 3A20.35
Purpose
To demonstrate horizontal simple harmonic motion of a mass held by two springs
Description
An air track cart, connected by springs to two fixed points, is set into simple harmonic motion about its equilibrium position. Additional masses can be added to the oscillating air track cart to decrease its frequency of oscillation.
Equipment
Air Track & Accessories, mini-springs
Support Equipment
Air Supply
Simple Harmonic Motion: Oscillations
PASCO Sc Wksp: SHM
PIRA Class: 3A40.05*
Purpose
To graphically observe the simple harmonic motion of a mass on a spring.
Description
Observe the real time displacement, velocity & acceleration of the motion of a mass on a spring.
Equipment
Various springs (or slinky hung from ceiling), masses
Support Equipment
Ring stand, Motion Detector, PASCO Sc. Wksp. Interface and auxiliary computer & cart
Driven Mechanical Resonance: Oscillations
Tacoma Narrows film
PIRA Class: 3A60.10
Purpose
To observe the energy transferred to an object due to driven mechanical resonance
Description
A film of the collapse of the Tacoma Narrows bridge due to driven mechanical resonance.
See film text below.
Support Equipment
Classroom Projector and Video cassette player
Film Text:
”The main span of the bridge near Tacoma, Washington was 2800 ft long, 39 ft wide, and the steel stiffening girders (shown during construction) were 8 ft tall. The bridge was opened for traffic on July 1, 1940. In the four months of active life of the bridge before failure, many transverse (vertical) modes of vibration were observed before November 7, 1940. The main towers were nodes, of course, and between them there were from 0 to 8 additional nodes. Maximum double amplitude (crest to trough) was about 5 ft in a mode with 2 nodes between the towers; the frequency of vibration at that time was 12 vib/min.
Measurements made before failure indicated that higher wind velocities favored modes with higher frequency. This correlation may be explained by the fact that turbulent velocity fluctuations of winds can be considered as composed of a superposition of many periodic fluctuations, and the fluctuations of higher frequency are preponderant at higher wind velocities. There was no correlation between wind velocity and amplitude of vibration. Early on the morning of November 7 the wind velocity was 40 to 45 mi/hr, perhaps larger than any previously encountered by the bridge. Traffic was shut down. By 9:30 a.m. the span was vibrating in 8 or 9 segments with frequency 36 vib/min and double amplitude about 3 ft. While measurements were under way, at about 10:00 a.m., the main span abruptly began to vibrate torsionally in 2 segments with frequency 14 vib/min. The amplitude of torsional vibration quickly built up to about 35 degrees each direction from horizontal. The main span broke up shortly after 11:00 a.m. During most of the catastrophic torsional vibration there was a transverse nodal line at mid-span, and a longitudinal nodal line down the center of the roadway (the yellow center stripe!). Note that Prof. Farquharson sensibly strides (?) down the nodal line as he leaves the bridge after making observations.
The crucial event at 10 a.m. What directly led to the catastrophic torsional vibration was apparently the loosening in its collar of the north cable by which the roadway was suspended. The center of the cable was moving back and forth relative to the center of the suspended span. This allowed the structure to twist. The wind velocity was close enough to the critical velocity for the torsional mode observed, and the vibration built up by resonance and was maintained until collapse inevitably took place.
The bridge was rebuilt using the original anchorages and tower foundations. Studies at the University of Washington Engineering Experiment Station resulted in a design for the new bridge, which used deep stiffening trusses instead of girders. The new bridge is entirely successful.”
Coupled Oscillations: Oscillations
Coupled Pendula
PIRA Class: 3A70.20
Purpose
To demonstrate motion coupling between two pendula of the same length.
Description
Observe the energy transfer between "linked" masses
Different set-ups are available:
- A set of six masses mounted on top of different length rigid wires
- Masses suspended from different length strings
Equipment
Coupled pendula
Support Equipment
Spring stand
Coupled Oscillations: Oscillations
Horizontally Coupled Masses on Springs
PIRA Class: 3A70.46*
Purpose
To demonstrate coupled oscillations in a system of two identical coupled air track gliders.
Description
Two moveable air track gliders are connected by three mini-springs to fixed end points. Pushing one of the gliders causes motion that couples back and forth between the two gliders. Giving the two gliders the same initial displacement (in phase, or out of phase) can excite two normal modes.
Equipment
Air Track & Accessories, Mini-springs
Support Equipment
Air Supply
Coupled Oscillations: Oscillations
Vertically Coupled Masses on Springs
PIRA Class: 3A70.47*
Purpose
To demonstrate motion coupling between spring pendula.
Description
- Suspend various masses from various springs
- Set one mass into vertical SHM
- Observe any coupling motion between the mass given initial motion and masses with like resonance modes
Equipment
Coupled Masses on Springs
Support Equipment
Ring Stand
Transverse Pulses & Waves: Wave Motion
Pulse on a Rope
PIRA Class: 3B10.10
Purpose
To observe the transfer/ motion of a single pulse on a rope
Description
Jerk the end of a (rubber) rope to create a pulse. Vary the tension in the rope to vary the speed of the pulse.
Equipment
Rubber Rope tied to a fixed endpoint
Transverse Pulses & Waves: Wave Motion
Human Wave
PIRA Class: 3B10.12*
Purpose
To demonstrate a transverse wave.
Description
Reference is made to the human wave seen at stadiums.
- Have students (beginning on one side of the room) lift their arms up into the air – one row at a time.
- Have students continue the “reflection” of the wave when it reaches the opposite end of the room.
Equipment
Large class of students
Transverse Pulses & Waves: Wave Motion
Slinky on a Table
PIRA Class: 3B10.20
Purpose
to observe the change in a medium (slinky) when a portion of that medium (slinky) is displaced perpendicularly from its equilibrium position
Description
With a 6' slinky on a table, demonstrate a transverse pulse/ wave.
Equipment
6’ Slinky
Transverse Pulses & Waves: Wave Motion
Standing Pulse
PIRA Class: 3B10.25
Purpose
Description
Equipment
Two long elastic tubes
Support Equipment
Transverse Pulses & Waves: Wave Motion
Vertical Rods Wave Model
PIRA Class: 3B10.50
Purpose
To observe a model of a transverse wave.
Description
Model is hand-cranked to show a set of vertical rods’ transverse motion.
Equipment
Vertical Rods Wave Model
Transverse Pulses & Waves: Wave Motion
Wave Generator, driven
PIRA Class: 3B10.60
Purpose
To observe standing
Description
Waves with different wavelength are mechanically generated using wave generator, string and counter weights.
Equipment
Wave Generator
Support Equipment
Longitudinal Pulses & Waves: Wave Motion
Slinky on a Table
PIRA Class: 3B20.12
Purpose
To observe the change in a medium (slinky) when a portion of that medium (slinky) is displaced parallel to its equilibrium position
Description
With a 6' slinky on a table, demonstrate a longitudinal pulse/ wave.
Equipment
Slinky
Longitudinal Pulses & Waves: Wave Motion
Longitudinal Wave Model
PIRA Class: 3B20.30
Purpose
To observe a model of a longitudinal wave
Description
Longitudinal waves or pulses can be manually produced with this model. One end of the model can be clamped to simulate a closed tube.
Equipment
Longitudinal Wave Model
Support Equipment
Longitudinal Pulses & Waves: Wave Motion
Vertical Rods Wave Model
PIRA Class: 3B20.50
Purpose
To observe a model of a longitudinal wave.
Description
Model is hand-cranked to show a set of vertical rods’ longitudinal motion.
Equipment
Vertical Rods Wave Model
Standing Waves: Wave Motion
Rope Standing Wave
PIRA Class: 3B22.20
Purpose
Using only a long, simple rope, observe standing waves
Description
Having a student hold one end of the rope firmly, shake the other end to generate standing waves. Try alternating the frequency of your hand’s vertical motion to produce other harmonics on the rope.
Equipment
Rope
Support Equipment
Optional: Stroboscope
Standing Waves: Wave Motion
Wave Generator
PIRA Class: 3B22.22*
Purpose
To observe standing waves on a string
Description
Wave Generator drives one end of a string with the other end attached to a hanging mass. Driving frequency can be varied and a strobe light can be used to view the resulting standing waves
Variation:
Change the tension of the string by adding or removing masses.
Equipment
Frequency Wave Driver, Generator & String
Support Equipment
Ring Stands, Pulley, 150 - 200g mass
Standing Waves: Wave Motion
Slinky Standing Waves
PIRA Class: 3B22.50
Purpose
Using only a long, simple slinky, observe longitudinal or transverse standing waves
Description
With a 6' slinky on a table, demonstrate a standing wave.
Equipment
Slinky
Standing Waves: Wave Motion
Standing/Traveling Wave Model
PIRA Class: 3B22.80
Purpose
Description
Crank the model to observe the difference between standing and traveling waves.
Equipment
Standing/Traveling Wave Model
Support Equipment
Overhead projector
Wave Properties of Sound: Wave Motion
Bell in a Vacuum
PIRA Class: 3B30.30
Purpose
To demonstrate that sound waves require a medium for propagation.
Description
Start the bell for students to note the sound of the bell under the bell jar.
- Turn pump on, wait ~ 2 minutes to produce a good vacuum, during which the sound intensity will decrease
- Turn off vacuum pump and slowly let air back into bell jar, during which the sound intensity will increase
Equipment
Bell jar & doorbell
Support Equipment
Vacuum pump
Wave Properties of Sound: Wave Motion
How to Talk like a Duck
PIRA Class: 3B30.50
Purpose
Description
Show the dependence of pitch of sound on its medium.
Equipment
Lg plastic trash bag w/ hose & clamp
Support Equipment
Helium gas
Doppler Effect: Wave Motion
Doppler Reed
PIRA Class: 3B40.25
Purpose
To demonstrate the Doppler effect.
Description
Hear the shift in frequency of pitch as Doppler Reed rotates.
Equipment
Doppler Reed
Support Equipment
Rotation Motor
Doppler Effect: Wave Motion
Doppler Football
PIRA Class: 3B40.35*
Purpose
To demonstrate the Doppler effect.
Description
Hear the shift in the sound wave frequency as the Doppler ball passes by.
Equipment
Doppler Football
Doppler Effect: Wave Motion
Doppler Tuning Fork
PIRA Class: 3B40.40*
Purpose
To demonstrate the Doppler effect.
Description
Hear the shift in the frequency of the sound wave as a tuning fork is spun overhead.
Equipment
Tuning Fork on a String
Interference & Diffraction: Wave Motion
Ripple Tank Film loops
PIRA Class: 3B50.30
Purpose
Description
Equipment
Support Equipment
Laser Disk Player
Interference & Diffraction of Sound: Wave Motion
Two Loud Speakers
PIRA Class: 3B55.10
Purpose
To observe the interference of sound waves
Description
The same note is played off of a keyboard into tow speakers
The position of one of the speakers is shifted back and forth, while seated students hear the sound intensity of the interfering waves increase and decrease.
Equipment
Keyboard and speakers
Beats: Wave Motion
Beat Forks
PIRA Class: 3B60.10
Purpose
To illustrate the beats produced by two similar tuning forks
Description
Two dissimilar tuning forks mounted on resonance boxes are struck producing audible beats.
Equipment
Tuning forks on resonance boxes and rubber mallet
The Ear: Acoustics
Model of the Ear
PIRA Class: 3C10.10
Purpose
To illustrate the parts of the ear, their spatial relationships, and their functions.
Description
Model shows the major organs of the ear including the bone chain, the cochlea, and the semicircular canal assembly.
Equipment
Ear model
Pitch: Acoustics
Pitch Range Chart
PIRA Class: 3C20.05*
Purpose
Description
Equipment
Pitch range chart
Support Equipment
Intensity & Attenuation: Acoustics
Decibel of Sound
PIRA Class: 3C30.10*
Purpose
To observe the change in the reading of a (digital) decibel meter as sound loudness increases.
Description
Use the digital sound meter to measure sound intensity
- Have students clap, first softly then gradually louder and louder
- Have one student clap loudly, starting right beside meter and gradually increase the distance between his/ her hands and the meter.
(Use the overhead camera in the large classrooms to show the meter display)
Equipment
dB Meter
Architectural Acoustics: Acoustics
Reverberation Time or “Slapping Boards”
PIRA Class: 3C40.10
Purpose
Study the reverberation time of a room.
Description
Clap boards to generate sound for measuring/ observing reverberation time.
Equipment
Slapping Boards
Music Perception and the Voice: Acoustics
Tuning Forks on Resonance Boxes
PIRA Class: 3D46.16
Purpose
A tuning fork mounted on a box (one end closed) causes box to resonant at the frequency of the fork.
Description
- Using two tuning forks (of the same frequency), each mounted on their respective box, (box openings facing each other) strike one of the forks. If you stop that fork after a few seconds, you will hear the same tone coming from the other fork, set into vibration by the first one.
Equipment
Tuning forks mounted on boxes, rubber mallet
Music Perception & the Voice: Acoustics
Keyboard and Oscilloscope
PIRA Class: 3C55.74
Purpose
To observe the waveforms of various sounds.
Description
Equipment
Keyboard, Speakers, Oscilloscope (or computer “Wave” program & microphone), Projector camera
Resonance in Strings: Musical Instruments
Sonometer
PIRA Class: 3D20.10
Purpose
Investigate the dependence of pitch on the length, tension and thickness of a string.
Description
A sounding box with strings, & adjustable bridges.
Equipment
Sonometer
Resonance Cavities: Musical Instruments
Resonance Tube w/ Piston
PIRA Class: 3D30.15
Purpose
To demonstrate the resonance of sound in an open or a closed cylindrical tube.
Description
Mount a microphone on a piston that slides in a glass tube and close the other end of the tube with a speaker.