90. Resonance

1. The Driven Mass on a Spring can be easily set to resonance. Measure the natural period with the LED readout and then drive at the inverse, the natural frequency, also measured by the LED readout. Or adjust the phase between the driver and oscillator to 90 degrees lag as shown by the phase readout.

2. Resonance can also be found for the Driven Torsion Pendulum. This is a little more difficult since there are no electronic readouts and the Q of the torsion wheel is quite large.

3. The Driven Tuning Fork demonstrates resonance at high Q. as the frequency synthesizer is adjusted in steps of 0.1 Hz near its resonant frequency.

4. In Beats and Sympathetic Vibration, see show how one vibrating tuning fork can acoustically induce vibrations in another nearby, if it is tuned to the same frequency.

5. A dramatic demonstration of resonance in Breaking Glass with Sound.

Along with this we have the Tacoma Narrows Bridge collapse on video.

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6. The Pasco track can be connected to a sinusoidal drive to demonstrate a driven simple hormonic oscillator. When the motor drive matches the resonance of the system, energy gets pumped in and the amplitude of the oscillations grow dramatically. This system can also be used to show a critically damped and under damped system by bringing an aluminum sheet close to two magnets attached to the cart.



7. A new demonstration is "resonance strips". Several metal strips of increasing length are bolted together in a star shape. When the device is vibrated with a mechanical driver controlled by a signal generator, the different strips come to resonance in the range 10 50 Hz by vibrating strongly at different frequencies according to their lengths. The class can see the frequency of the driver on a large display frequency counter.

8. The mechanical driver will also vibrate a ten inch wire loop, and will induce standing waves with 3, 5, 7, etc. antinodes around the circle at specific increasing frequencies. Rudnick's String shows the same effect on a linear string.