PROBLEM: To find the length of the air column, that will resonate with a vibrating tuning fork.

MATERIALS: For Christian schools; Tuning forks, graduated cylinder, beaker, water, metric ruler, and centigrade thermometer.

For Home School; You can use the 8 inch pipe from the stand of the SBB Balance. I have tried the 1/2 inch pipe from the thick wall pipe and the thin wall, both will work. The best results would be obtained from using a cylinder from a spent Caulking cartridge ( made of vinyl type of material )See a friendly painter; or see a friendly plumber for plastic piece of tubing, used under the sink for draining. You will have to attach a metric strip on to the cylinder for an accurate reading, so that you can read the length of the column. Least best, is to make markings on the side of the cylinder, with a fine point magic marker. If you do not have a centigrade thermometer, then use your Fahrenheit scale and see the conversion scale or formula, below.

To convert °F to °C , °F = ( °C X 9/5 ) + 32°

To convert °C to °F, °C = 5/9 ( °F - 32° )

Since the Resonance is so strong, you may want to try this method as well, place the speaker near by the water container. Place your ear over the cylinder as you lower it into the water, and you will hear the resonating sound that way. Have some look at the you and the cylinder, so that they can get an accurate reading of the height of the column.

Inside Diameters for:

Thin wall pipe from SBB stand = 1.8 cm

Thick wall pipe from SBB stand = 1.6 cm

Cylinder from a spent Caulking Cartridge = 4.7 cm *This is the one used in this experiment.

PROCEDURE AND OBSERVATION:

1. Hold a vibrating tuning for over the graduate cylinder.

2. Now, slowly pour water into the graduate cylinder, until an intense sound is heard.

3. If to much water is pour in, the effect is destroyed and you must repeat step # 2.

3b. Using the computer speaker ( you may want to turn the volume down for the other speaker ) and holding the speaker in one hand and the Cylinder in the other hand move both of them until you hear resonating sound. Try to keep the speaker close to the cylinder.

3c. When ready for tuning fork sound , go to bottom and hit link " A ".

4. Once you have found the level at which the air column will resonate.

5. Record the frequency of your tuning fork: 697 Hz

6. Record the temperature of the room. ___________ ° C

7. Record the length of the air column. The distance from the top of the graduated cylinder to the water level. ___________ cm

8. Now, check your answer by reading the following explanation and using the following formula.

Let a and c represents the extreme positions of a vibrating ends of the tuning fork. When the prong travels from c toward a, it sends a compression down the cylinder tube. If the sound of the fork is to be reinforced, this compression must be reflected by the water back to the end of the fork just in time to unite with the compression produced above the end of the fork just in time to unite with the compression produced above the end of the fork as it swings back toward c. Since the motion of the end of the fork c to a is half a complete vibration, the distance down the tube and back again must be half a wave length of the sound produced. Thus, the length of the air column must be a quarter wave length. The diameter of the cylinder also effects the length of air column needed. Two-fifths ( .4 x D ) of the diameter ( D ) of the cylinder should be added to the length ( L ) of the air column to obtain a quarter wave length of sound. ( D ) Diameter of the Cylinder from a spent Caulking Cartridge = 4.7 cm X two fifths ( .4 )= 1.88 or 1.9 cm

Speed of sound in air at 25 ° = 346 m/sec

Speed of sound in air at 0 ° = 331.5

	Speed of sound			Speed of sound
Wave length    =	----------------	or	Frequency    =	----------------
	Frequency			Wave length

Be sure to change centimeters to meters!!!!!

	331.5 meters + ( .6 meters X temperature )
Frequency         =	---------------------------------------------
	4   X   ( 1.9 cm + Length of air column )

QUESTIONS:

1. Explain the difference between constructive and destructive interference. Give examples of each.

2. Define resonance.

3. If velocity is constant, what happens to the wavelength as frequency increases.

4. On what two factors does the speed of sound wave depend?

5. If the amplitude is increased will the wavelength increase ? Explain.

6. Approximately how long is the delay between a gun shot and its echo heard from a mountain 5 miles away. ( the air temperature is 34 ° C )

7. Find the length for two other tuning forks, " B " and " C ".

Bridge in Tacoma, Washington state in 1940 collapse, wind on the bridge happened to match the natural vibration of the bridge and produced one disastrous resonance effect.

Even today, when an army crosses a bridge, they are always told not to march in step, but to brake step, or randomly march across the bridge, a lesson learned from the Tacoma bridge.

Are there any similarities between Tacoma bridge and the walls of Jericho?

Tuning fork A Tunning Fork A

Tuning fork B Tunning Fork B

Tuning fork C Tunning Fork C

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