1. The tuned-in washers. (#10) (Similar to the hanging pop cans) Top

This demonstration is another excellant illustration of the phenomenon of resonance. Whincrease en washer No, 7 starts to swing, washers Nos. 2 and 4 will swing with it. Washer No. 7 can be compared with the source of vibration and washer Nos. 2 and 4 are "tuned in" with or have the same frequency of vibration as washer No. 7. The same happens when washers 2 and 4 is started with the swinging first. The washers that have the same string length will swing with the original "swinger." So when washer No. 1 is started to swing, the only washer No. 3 will swing with it.

In resonance, the resonating object has to have the same frequencyof vibration as the source. Sometimes the source of vibration can be the object itself and then it will increase it's own vibrations. This was the case with the collapsing Tocoma bridge in Washington state, which started to vibrate because of a high wibd that blew against the bridge.

1. Why did washer number 2 and number 4 swing with number 7? Answer - They have the same length of string or more importantly will create the same frequency.

2. If washer number 2 were swinging first, which washer would swing with it? Answer - Numbers 4 and 7.

3. If washer number 1 were swinging first, which washer would swing with it? Answer - Number 3 should swing since the length is the same.

4. How can we compare this event with a sound source and resonating boxes? Answer - With a little bit of effort one wave can create a new wave (resonate) or add to an existing one.

Comments;

The movie of the bridge above is the Tacoma Narrows bridge. Your example of the "The Tuned-In Washers" is exactly what happened to that bridge. One cable started vibrating from the wind and the vibrations sent the same frequency of wave to the other cables holding the bridge up. This is the reason you're not suppose to swing or bounce on a chair lift. But if you do happen to start swinging your feet what would happen to the people in front or in back of you?

The Swinging book (#9) Top
This is an excellent wave to demonstrate resonance. There is always a source or orgin of the vibration and object which is resonating with the source. The huffing against the book can be compared the source of vibration oand teh swing of the book as the obect which resonateds with the source. When huffing is in phase with the swinging book it will swing higher and higher. In sound terms: when the source has the same frequency as the vibrating object, it will resonate with the sound source. In order to stop the swinging book, the huffing has to be done out of phase with the swinging.

1. Why is it not possible to blow the book to 45 degrees from the veritcal line one huff? Answer - You're not strong enough and can't blow that hard!

2. What is most important to get swinging higher and higher with the huffs? Answer - Timing your puff when the book is on the way down from the side you are blowing. (Just like pushing some one on the swing set).

3. How can we stop the swinging without touching the book? Answer- Start blowing on the book when it starts its way down from the other side. Do not blow on the book when it is on the way down. Or, blow the same way from the other direction side.

4. How can we compare the swinging of the book and the blowing, with sound and resonance? Answer - This also increases the energy of the wave with very little input or energy.

Comments;

Just like a regular swing set. Your pushes should be at the top of the swing as the object starts to fall. To slow it down you would start your "huff" on the opposite side when the object is on the way down.

The Singing Rod (or Resonating bar) (#11) Top
The rubbing of the bar made the cloth slip and grab, slip and grab, slip and grab alternately, causing the longitudinal (compression) or legthwise wave in the bar. The tapping at the end of the bar causes the same longitudinal wave, which will travel throught the whole bar, not only on the side where the vibration originated. This is why the vibration can be stopped by holding even the end of the bar that was not rubbed. When the bar is hit on the side instead of at the end, a transverse wave is created, which has a much longer wavelength and thus a much lower tone or pitch compared the longitudinal wave.

1. What did the rubbing of the bar do to it? Answer - Created a slip grab, slip grap pattern. The rosin made this work even better.

2. Why does the rubbing as well as the tapping produce the same tone in the bar? Answer - It is the same longitudinal (compression) wave.

3. Would hitting the bar on the side produce the same tone? Answer - No. It created a lower transverse wave.

4. Why can the vibration be stopped on the side of the bar that was not rubbed or hit? Answer - Because the wave is traveling the whole distance of the bar.

Comments:

This is so cool. I always wanted to do field trip to the Home Depot and get as many of their metal rods singing as we could!

The Multiple toning pipe (#12) Top

1. Why did the pipe give different tones? Answer - Because of the length of the wavelength.

2.  Did holding the pipe at different spots determin the tone? Answer - Yes.

3. Could the vibration continue by holding the pipe at more than one spot? More than two spots? Which of the spots? Answer - Technically yes, but this is pretty hard to do. You would have to hold the pipe at the nodes where the pipe is already not moving.

4.  Holding which of the spots would give the same tone? Answer - Spots 13 and 39 cm from the center.

5. Holding which of the spots on the pipe would give the hightest pitch? The lowest pitch? Answer - Highest pitch - spot 13 and 39 cm. Lowest pitch - spot 25.)

The Singing glass (#8) Top
When the finger is rubbing against the rim of the glass, it is not supposed to just slide over it, but catches and slides in very quick succession . It is just hitting the side of the glass with a hard object, softly and in very quick succession. It almost works like a bell hammer. As soon as the first few vibrations are produced, they make the glass resonate, because the pitch produced is exactly the same as that of the glass itself. By adding water to the glass, the vibrating mass increased and thus the pitch got lowered.

1. What is the purpose of the vinegar? Answer - It should have created some friction similar to the rosin on the resonating bar. Your finger needs to catch slide, catch slide....
In class we did not use vinegar since most students were able to do this without it.

2. Why do the hands and glass have to be clean? Answer - To get rid of any oils on your fingers.

3. What is the finger actually doing when it rubs the glass rim? Answer - Vibrating. slip grab, slip grab...

4. What is the pitch doing when water is added to the glass? Answer - The pitch would get lower.

Comments;

Tibetan Monks do the same sort of thing using something that looks like a metal pan and a wooden spoon. You can do this at home or when you're out for dinner to everyones amazement. Be sure to explain it them as well.

In the second video watch as the waves in the water follow the finger around.

The Resonating boxes (#14) Top

Answer to questions

1. Describe what happens. Answer - When one tuning fork is made to vibrate it sends a sound wave to the other and that one vibrates due to resonance.

2. The longest distance has been 14 meters! Answer - Your answer needs to be a measurement It should be in metric as any good science student!

3. Why can you not move the box any further and still hear the tuning fork? Answer - The sound wave loses energy and does not transfer any further.

Comments;

Many of your said you have seen this at home with your musical intruments (guitars and drums). Yep it is the same thing.