Phy 201
Your 'pearl pendulum' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** Your general comment, if any: **
** Your description of the rhythm of the pendulum when tilted 'back' **
When the bracket is tilted in the backward position the sounds are closer together and the number of bounces are less than the vertical model. I get about 8 bounces in the backward tilted model and around 10 in the vertical model before the pearl comes to a halt.
** Your description of the rhythm of the pendulum when tilted 'forward' **
With the bracket tilted in the forward position the rhythm tends to slow down as opposed to speeding up and the number of bounces are about 12 before the pearl stops touching the bracket and making a noise.
** Your description of the process used to keep the rhythm steady and the results you observed: **
I put a quarter under the backend of the bracket to just slightly tilt the bracket forward. I did this because in the before experiment the pearl bounces seem to get slower and when the bracket was vertical the pearl boucnes were faster. I needed to divide the distance between the two to get a steady beat. The beat was steady because as the pearl slowed down it bounced less distance it hit the bracket at almost the same time as it hit when it was faster and traveled more distance. I counted about 11 hits per try.
** Your description of what happened on the tilted surface (textbook and domino), rotating the system 45 degrees at a time: **
First position was with the pendulum tilted forward on the textbook with the dominos to the backend of the bracket. Basically the face or the business end of the pendulum where the pearl bounces was tilted forward. I ran the experiment and got about 15 bounces and the pearl tended to slow down.
Second position I turned the pendulum counter clockwise as instructed with the bounce face tilted sideways instead of forward or backward. I got about 10 bounces and the sound tends to speed up.
Third position I turned the pendulum counter clockwise once more and the face where the pearl bounces is tilted backward. I ran the experiment and I get the least amount of bounces of about 8 and the bounces tend to be faster before the come to a halt.
The last position I turn the pendulum counter clockwise and now the face is tilted to the side again and the results are the same as it was with it tilted to the other side. I get somewhat faster bounces and sounds before the pearl comes to a halt.
** Your description of how you oriented the bracket on the tilted surface to obtain a steady rhythm: **
To get the most regular beat I would tilt the pendulum or the face where the pearl hits forward. If it was allowed I would turn the pendulum like a dial on the slooped surface to where it might be at 22degree angle or so and run a number of experiments until I got the most regular beat.
** Your report of 8 time intervals between release and the second 'hit': **
.578
.609
.625
.547
.421
.578
.516
.594
The numbers where between .421 and .625 and I tried my best to be consistant with my method of college data. However, I can't help but think that the human element of collecting this data is some of the reason I get some differences in my times.
** Your report of 4 trials timing alternate hits starting with the second 'hit': **
.640, .640, .625, .687
.515, .718, .687, .687
.562, .656, .75, .703, .656
.625, .625, .75, .656, .671
My results indicate if I collected the data properly that the pendulum has a steady beat until it comes to a halt.
** The length of your pendulum in cm (you might have reported length in mm; the request in your instructions might have been ambiguous): **
96.62mm
** Your time intervals for alternate 'hits', starting from release until the pendulum stops swinging: **
I'm not the best at this experiment as my hand eye cordination is a little off. It's very hard for me to collect this data but my second set of times seems to fit the best.
.515, .718, .687
** Your description of the pendulum's motion from release to the 2d hit: **
The motion of the pendulum starts at its most extreme point and gravity pulls it to its equilibrium point which would be straight down.
** Your description of the pendulum's motion from the 2d hit to 4th hit: **
Once the pendulum is released from its extreme point it is pulled to its natural resting postion or the equillbrium. However, the force of motion keeps the pendulum from resting until its energy is exhausted. This keeps the pendulum in motion and strikes the bracket and sends it back to toward its starting position. By striking the bracket some of the energy is lost and the pendulum doesn't quiet have enough motion energy to get back to its original starting position but pretty close. It then begins to fall again to find its natural resting position. As it starts its journey back down the second time the pearl does not have the same amount of motion energy as it did the first trip.
** Your description of the difference in the pendulum's motion from release to the 2d 'hit', compared to the motion from the 2d 'hit' to the 4th hit: **
By the time the pearl gets to its forth hit it has lost a good deal of its original energy and is making shorter trips to its starting point and its resting spot.
** Your description of the difference in the pendulum's motion from the 2d to the 4th 'hit' compared to the motion from the 4th to 6th hit: **
Same as the previous question, the pearl by the sixth hit is almost at rest and is traveling even less distances. Even though it might still be hitting the bracket it's much slower in motion but travels less distance and therefore seems to have the same consistant beat when hitting the bracket.
You give excellent descriptions, but you didn't include the most important point. If a phase of motion refers to motion from an extreme position to the equilibrium position or vice versa, then between release and the second hit there are three phases, while between the second and the fourth hit there are four phases. If the rhythm is constant, then it is reasonable to conjecture that the time required for a phase is always the same, or very nearly so. Thus times between alternate subsequent hits will be greater than the time between release and the second hit, which is consistent with your observations.
** Your conjecture as to why a clear difference occurs in some intervals vs. others: **
The initial speed might be faster and the full potential energy may cause a slight faster time than the rest of the time intervals.
** What evidence is there that subsequent intervals increase, decrease or remain the same: **
I think if the pendulum was balanced just right that you would get a steady time interval between hits of the pearl.
** What evidence is there that the time between 'hits' is independent of the amplitude of the swing? **
I don't think the actual length plays a big part in the pendulum's swing. As long as you have adequate string length to where it has room to move you should get fairly same results. However, of coarse if your string was one inch long don't expect to get any kind of results.
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over an hour and a half!
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&#This looks good. See my notes. Let me know if you have any questions. &#