The Resonance Project

The Resonance Project uses CoachLab probeware in order to teach the concept of resonance to  High School or College level students.  The Resonance Project includes the electronic project files that can be used with Coach Software as well as a special piece of apparatus for measuring and creating resonance in a spring and mass system.  This project requires the use of a force sensor. Students perform several experiments to learn about resonance and natural frequency including: 1. Introduction (Students watch video clips and are introduced to the collapse of the Tacoma Narrows bridge) 2. Natural Frequency (Students make measurements and manipulate the data in order to determine the natural frequency of a tuning fork) 3. Spring Oscillations (Students make measurements and manipulate the data in order to determine the natural frequency of a spring and mass system) 4. Forced Oscillations (Students use Coach's control capability in order to send pulses to a coil that drives the spring and mass system into chaotic, damped and resonant oscillations) 5. Resonating Bridges (Students watch a video and learn how pulses of air caused the Tacoma Narrows bridge to collapse due to resonance) 6. Modeling (Students use modeling  to describe the force on the spring and mass system as it is driven into resonance) 7. Assessment (Students relate what they have learned to sound waves breaking glasses and answer questions about their experiments)

The Resonance project's apparatus (pictured above right) uses a mass made up of a special weight hanger that can has a ceramic magnet and can accommodate differing numbers of washers in order to vary the mass from experiment to experiment.  Oscillations in the spring and mass system are measured using a commonly available force sensor (pictured at the top of the apparatus.  The mass and spring are suspended in a clear plastic tube mounted to a base with three adjustable feet to keep the system level.  A coil is mounted around the tube and can be moved up and down to allow for different length springs or higher mass systems.  The coil is driven by 12 Volt 1 Amp pulses from the CoachLab II interface panel.  A program to control the pulses to the spring in this activity is already written and can be found in the "Forced Oscillations" activity.

Students use this apparatus for two experiments.

1) Students manually set the spring and mass system into oscillations and then measure the oscillations using the force sensor.  The natural frequency of the system can then be determined by graphical means, or by using Coach software's signal analysis tool.  Students can also note the damped nature of the oscillations over time and can learn that without external energy the system will eventually stop oscillating due to internal resistance to deformation in the material that makes up the spring.

2) Students then use Coach to drive the system via pulses to the coil.  Since the mass system includes a magnet, then pulses of electricity in the coil can drive the system into motion.  Students can vary the pulse length and frequency to try to match their predicted natural frequency of this system.  If the frequency is off by a fractional amount above or below resonant frequency then they can observe damped oscillations and chaotic oscillations.  Students can then learn that to keep the spring and mass system oscillating not only must external energy be added to the system to make up for the damping effect of the spring's internal resistance, but that that frequency must be applied in pulses that are equal to the natural frequency of the system or else they will interact with the spring to dampen it, or drive it into wild oscillations that are out of control. 

These experiments are supported by other experiments into natural frequency, as well as multimedia presentations showing the consequences of resonance in the real world such as the disaster of the Tacoma Narrows Bridge. 

Teachers at college level with more advanced students might also want to use this activity to introduce the concepts of differential equations and how they are used in predicting systems natural frequency and methods to dampen oscillations in things like bridges or airplane wings. 

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