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3D40.55-Break the Beaker

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Video:

Description: This demonstration shows the importance of resonance.
By sending powerful sound waves at the resonant frequency of the beaker, you can shatter it.

Equipment:

  • Break the Beaker apparatus
  • Function generator
  • Amp
  • Oscilloscope
  • Mic with 9V battery
  • Beaker

Setup Procedure:

  1. Attach a 9V battery to the mic (this is needed).
  2. Turn on all the equipment. Make sure the Mic is CH2 and the function generator is CH1 on the oscilloscope.
  3. Make sure the function generator is set to -20dB attenuation if using the Samson amp.
  4. If using the Samson amp, connect the function generator as input 1 not in bridged mono mode (bridged mode is too much amplification). Connect the speaker to output 1.
  5. Set the oscilloscope to view the function generator (such as can be seen in the last picture).
  6. Prop the beaker up on the metal holder on top of the styrofoam. Point the lip of the beaker at the speaker.
  7. Aim the mic directly at the beaker and place it very close. Tap the beaker with the pencil and make sure you can view it on the oscilloscope.
  8. Try and tune the function generator to the resonant frequency of the beaker. Some fine adjustments will be needed in the classroom.
  9. Plug the apparatus in when in the classroom.
  10. When the professor is done, sweep out the broken glass.
  11. Take off the 9V battery.

Demonstration Procedure:

  1. Place the pencil in the beaker.
  2. Turn the amp volume (left knob) up a little (not to break the beaker).
  3. Make fine adjustments to the function generator until you can get the pencil to vibrate.
  4. Take the pencil out, and fine tune the frequency by viewing the oscilloscope.
  5. When you quickly turn the speaker up a bit and then off, you should see CH2 resonant for a second or two after the speaker is turned off. This means you are in tune.
  6. When ready to break the beaker, close the safety flap and warn students that this will make a loud noise.
  7. Quickly turn the volume up high then off. The beaker should break.
  8. Do not leave the speaker on for more then a second or two at most (or the speaker will break).
  9. If the beaker does not break, further fine tuning is needed.
  10. When finished, turn off all equipment.

High Noise Level High Noise Levels
Hearing protection is recommended.