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3D40.55 - Shattering the Wine Glass

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​3D40.55 - Shattering the Wine Glass

Title3D40.55 - Shattering the Wine Glass

 This demonstration drives a wine glass acoustically until it shatters.

Assembly Instructions

The demonstration lies on a cart that is ready to be rolled out for lecture.  Make sure there is ear protection for the lecturer and enough (2-3 per class section) tuned glasses to get through the lecture.


Setup Time10
Operation Time10
Preview Time10
Operation Instructions

To begin, turn on the video of the wine glass to the main projector and turn down the room lights.  Be sure to warn the students that the sound will be loud and to plug their ears if needed.  The next step is to tune the driving signal generator to the resonant frequency of the wine glass. 

When set, turn the amplitude of the signal on the amplifier until the power meter readys an output of 0.1W.  At this point, it is important to adjust the driving frequency of the signal generator while watching the oscilloscope to reach the highest peak (When the glass resonantes at the driving frequency, the piezo feedback pad that the glass resides on will register this as an increase in amplitude on the oscilloscope.). 

Once you feel that you have found the maximum amplitude oscillation of the glass, then adjust the strobe signal generator 2-6 Hz off of the resonant frequency that the glass is set.  At this point, you can blow up the wine glass by increasing the amplitude on the amplifier until the glass shatters. 

**Be sure to warn your students once more to cover their ears before you turn up the amplitude volume to shatter the glass**

Demo on DimeNo
PIRA 200Yes
Export Instructions (if different)
HazardsSound Hazard - Use Ear Protection

This demonstration shows the power of resonance in a driven oscillator.
The first concept is a natural frequency: objects have a preferred oscillation frequency dictated by the objects characteristics (such as shape and material). When the wine glass is flicked by a finger, it hums at its natural frequency. When a bell is rung, it reverberates at its natural frequency. When a pendulum is released from a height, it oscillates at its natural frequency. When you accidentally drop a pan and it rings for a moment until you touch it (damping it), it is oscillating at its natural frequency. The natural frequency is a characteristic of the system.
The amplitude of these natural frequency oscillations depend on the impulse that drives them into motion. The pendulum will swing higher (have a higher amplitude) if released from a greater height. A bell will ring quietly or loudly depending upon how hard it is hit. There are other ways to control (and enhance) the amplitude of an oscillation.
Oscillating systems can be driven. A common example of a driven pendulum is a swing. If you release a swing from a height, it will swing high for a time but quickly lose amplitude until it comes to a stop at its equilibrium point if it is not driven. This is fun, but I’m sure you’ve all learned that you can keep the amplitude of the swing high for a long time if you push it swing while it passes one of its two maximum points. This is an example of a driven oscillator.
Let’s start by measuring the natural frequency of the swing. Take a swing that completes one cycle per second. In other words, the swing takes one second to travel forward and then backward to the start point. Remember that the natural frequency of the swing depends on the length of the chains, not the starting point or how hard the initial push is. The natural frequency is 1 Hertz (Hz - one cycle per second).
We’ve learned from experience that good friends push the swing every time it swings back. If that is the case, then the event of pushing happens every second. We can describe the pushing as one event per second or as 1 Hz. This is the driving frequency of the system. This frequency works the best; the swing achieves the highest amplitude when the friend pushes every cycle.
Lesser friends may not be as interested and may push every other cycle (only half the time) which is a rate of 0.5 Hz. This means that the swing is not driven as ideally and will not maintain the amplitude of the system where the driving frequency matches the natural frequency. This is a pretty good system.
Over-eager friends may want to impress you and push at a rate of 3 Hz (three events per second). This will result in pushing two extra times for each useful push (or three times more work than necessary). On a swing this won’t diminish the amplitude, but in other systems the over-driving can diminish the amplitude.
And let us not forget our enemies who push every 1.25 seconds (0.8 Hz). This means that even though they push 4 times in 5 seconds, only one of those pushes will land at a good time to increase amplitude. When we complain that the pushing wasn’t that good, they’ll remind us how much work they did.
Achieving an optimal driving frequency for all oscillators is constrained by the similar factors for pushing a swing. See figure 1.
  • The ideal driving frequency is exactly the same as natural frequency of the system.
  • Driving at a fraction of the time is not as good, but can still produce amplitude (especially if it is a large factor such as a half or a third of the time).
  • Driving a multiple of the natural frequency will produce amplitude, but not necessarily the full amplitude.
  • Driving at a non-integer multiple is not a good driver and a waste of energy.
Anytime a system is driven in such a way that gives the oscillator large and sustained amplitude it is called resonance. When an oscillator is driven at resonance, the achieved amplitude can cause dramatic reactions. Rigid bells can crack, bridges can collapse, and wine glasses can shatter. Rigid systems with weaknesses tear apart with dramatic flair when the amplitude of the oscillation exceeds the systems ability to stay intact.
In the case of the wine glass, we use sound as the driving force. Each wine glass has a natural frequency that can be heard by dinging the glass. If we output sound from a speaker at the natural frequency of the glass, the glass will resonate with the sound waves and oscillations can be seen under a strobe. In fact, to find the exact frequency of the glass, we look for those high amplitude oscillations.

There are two amplitudes we consider, the amplitude of the driving force and the amplitude of the oscillations. It turns out they are directly related, if we set the amplitude of the driving frequency low, the amplitude of the oscillations will be low. If we turn the amplitude of the driver up high, it can result in the wine glass shattering due to the high amplitude oscillations of the glass.
To shatter a wine glass, we determine the natural frequency of the system, calibrate the driving frequency to match, and turn the amplitude of the driver up. This results in a high amplitude oscillation in the wine glass that will break it.
Concept Question: If the natural frequency of a swing is 24 Hz, which driving frequency will result in the highest amplitude: 6 Hz, 12 Hz, 36 Hz, 48 Hz, or 60 Hz?

Category3 Oscillations
Subcategory3D - Instruments
Keywordsresonance, wine glass, shatter, natural frequency, driven
Construction Information
watt meter
function generator and amplifier - pasco digital
strobe - frequency tunable clip-on
amplifier - Samson SX1200
piezo sensor
wine glass
audio driver - BMS Speakers, 8-ohm, mounted on plastic base
camera - b&w
ear protection
picture-in-picture unit
camera - USB, color, OSC Control camera
dust pan and brush