#$&*
course Phy 242
March 22 around 6:30pm.
Brief Rubberband-Chain Experiment 1B________________________________________
Using the same setup as in the preceding experiment, pulling back so that the center of the chain hangs about a foot lower than its ends, rapidly move your hand back and forth in order to get the chain wiggling. Unless you adjust the frequency of your back-and-forth motion, the chain will probably wiggle incoherently.
While still moving your hand at the same frequency, begin pulling back a little harder, which will lengthen the chain and might cause you to have to back up a bit. Gradually increase your pull, backing up as necessary.
At various lengths, if you continue with the same frequency, the chain's motion will become coherent. This will tend to modify the frequency of your motion. Most people will find the coherent motion of the chain more pleasant and will tend to unconsciously adjust the frequency to maintain that state as they continue to move back (this could in itself lead to an interesting experiment). Some might have an opposite reaction. Try to concentrate on maintaining a constant rhythm to your motions.
Report what you observe as you move back:
****
Having one end of the chain hooked stationary on something, I started out with it hanging about a foot lower than the ends and started my horizontal back and forth hand motion. The chain went crazy for a bit until I really concentrated and got a good rhythm going. I had several wavelengths. The more I get moving back, keeping the same rhythm as best as I could, I got to the point where I only saw one complete wavelength, stretched out. You could also see how the chain looked like 2 “eye” shapes, where it was going so fast, it looked cool. So the more I moved back, the faster it got and the waves got more narrow.
#$&*
Leave the rubber band out of it and just move your hand back and forth at the same frequency as before. Count the motions of your hand in a 1-2-3-4- rhythm, with one count for each complete back-and-forth motion. Practice until you can reliably count four 4-counts, then using the TIMER or a clock that displays seconds, take the data necessary to determine as closely as possible the frequency of your motion, in cycles per second (one cycle is one complete back-and-forth motion).
Report your data, and your frequency:
****
I used the TIMER program and timed my hand motion that I did on the rubberband chain. I did it quite a few times for more accuracy. Here’s my data:
0.203
0.204
0.203
0.203
0.203
0.187
0.204
0.203
0.218
0.188
0.203
0.203
0.203
0.203
0.204
0.203
0.203
0.203
0.203
0.188
0.218
0.203
0.204
0.203
0.203
0.203
0.203
0.203
0.203
0.203
0.204
I clicked the TIMER 28 times (1 being over and back) and got a 5.672 second interval. My data above looks pretty consistent and it looks like 0.203 was the most repeated.
#$&*
If you pull the chain back far enough, the entire chain will move back and forth as one, with the entire chain to the right at one instant, then to the left a short time later, and continuing to alternate in this manner.
Moving your hand back and forth at the same frequency as before, at what length does the chain best move in this manner?
****
I stretch the chain a little over 35 feet (11m), still using my same hand motion and rhythm as before, and still was seeing wavelengths rather than it moving back and forth as ONE. I did see that if I slowed down my “pace” then it would work. I want to try and go outside with it, having more room to move back, but it’s dark outside and I can’t see.
#$&*
At another length, still moving your hand with the same frequency, the chain will move in such a way that at any instant half the chain will be moving to the left while the other half moves to the right.
Moving your hand back and forth at the same frequency as before, at what length does the chain best move in this manner?
****
The chain starts doing this manner around 23 feet (7m), give or take a little, with my same back and forth frequency that I’ve been doing.
#$&*
You have observed the lengths at which two modes of chain vibration occur, at a common frequency. Other modes are possible. If you can observe them, do so and describe them, and give an estimate of the lengths at which these modes occur.
****
At 13.5 ft (about 4m) I got 3 waves with my same rhythm but as soon as I step back, it goes into just 2 big waves. It’s pretty cool to experiment with.
#$&*
*#&!
&#Very good data and responses. Let me know if you have questions. &#
#$&*
course Phy 242
March 22 around 6:30pm.
Brief Rubberband-Chain Experiment 1B________________________________________
Using the same setup as in the preceding experiment, pulling back so that the center of the chain hangs about a foot lower than its ends, rapidly move your hand back and forth in order to get the chain wiggling. Unless you adjust the frequency of your back-and-forth motion, the chain will probably wiggle incoherently.
While still moving your hand at the same frequency, begin pulling back a little harder, which will lengthen the chain and might cause you to have to back up a bit. Gradually increase your pull, backing up as necessary.
At various lengths, if you continue with the same frequency, the chain's motion will become coherent. This will tend to modify the frequency of your motion. Most people will find the coherent motion of the chain more pleasant and will tend to unconsciously adjust the frequency to maintain that state as they continue to move back (this could in itself lead to an interesting experiment). Some might have an opposite reaction. Try to concentrate on maintaining a constant rhythm to your motions.
Report what you observe as you move back:
****
Having one end of the chain hooked stationary on something, I started out with it hanging about a foot lower than the ends and started my horizontal back and forth hand motion. The chain went crazy for a bit until I really concentrated and got a good rhythm going. I had several wavelengths. The more I get moving back, keeping the same rhythm as best as I could, I got to the point where I only saw one complete wavelength, stretched out. You could also see how the chain looked like 2 “eye” shapes, where it was going so fast, it looked cool. So the more I moved back, the faster it got and the waves got more narrow.
#$&*
Leave the rubber band out of it and just move your hand back and forth at the same frequency as before. Count the motions of your hand in a 1-2-3-4- rhythm, with one count for each complete back-and-forth motion. Practice until you can reliably count four 4-counts, then using the TIMER or a clock that displays seconds, take the data necessary to determine as closely as possible the frequency of your motion, in cycles per second (one cycle is one complete back-and-forth motion).
Report your data, and your frequency:
****
I used the TIMER program and timed my hand motion that I did on the rubberband chain. I did it quite a few times for more accuracy. Here’s my data:
0.203
0.204
0.203
0.203
0.203
0.187
0.204
0.203
0.218
0.188
0.203
0.203
0.203
0.203
0.204
0.203
0.203
0.203
0.203
0.188
0.218
0.203
0.204
0.203
0.203
0.203
0.203
0.203
0.203
0.203
0.204
I clicked the TIMER 28 times (1 being over and back) and got a 5.672 second interval. My data above looks pretty consistent and it looks like 0.203 was the most repeated.
#$&*
If you pull the chain back far enough, the entire chain will move back and forth as one, with the entire chain to the right at one instant, then to the left a short time later, and continuing to alternate in this manner.
Moving your hand back and forth at the same frequency as before, at what length does the chain best move in this manner?
****
I stretch the chain a little over 35 feet (11m), still using my same hand motion and rhythm as before, and still was seeing wavelengths rather than it moving back and forth as ONE. I did see that if I slowed down my “pace” then it would work. I want to try and go outside with it, having more room to move back, but it’s dark outside and I can’t see.
#$&*
At another length, still moving your hand with the same frequency, the chain will move in such a way that at any instant half the chain will be moving to the left while the other half moves to the right.
Moving your hand back and forth at the same frequency as before, at what length does the chain best move in this manner?
****
The chain starts doing this manner around 23 feet (7m), give or take a little, with my same back and forth frequency that I’ve been doing.
#$&*
You have observed the lengths at which two modes of chain vibration occur, at a common frequency. Other modes are possible. If you can observe them, do so and describe them, and give an estimate of the lengths at which these modes occur.
****
At 13.5 ft (about 4m) I got 3 waves with my same rhythm but as soon as I step back, it goes into just 2 big waves. It’s pretty cool to experiment with.
#$&*
*#&!
&#Very good data and responses. Let me know if you have questions. &#