Phy 121
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: **
I just thought I would re-complete this project.
** Your description of the rhythm of the pendulum when tilted 'back' **
It tends to speed up. The rhythm of the pearl increases as time goes on. It hits the bracket more and more frequently.
** Your description of the rhythm of the pendulum when tilted 'forward' **
It hits the bracket less and less frequently with each bounce. The sound gets farther apart.
** Your description of the process used to keep the rhythm steady and the results you observed: **
I began by putting the bracket on the computer desk. I realized that it was not level because the string leaned one way, so I put the bracket on the floor. Then I noticed it was level and the pearl rested slightly against the bracket. After this, I noticed that the rhythm was steady and it bounced off the bracket six times.
** Your description of what happened on the tilted surface (textbook and domino), rotating the system 45 degrees at a time: **
On the first test, I put the front of the bracket with the pearl facing the end of the book with the two dominoes stacked. The sound from this got closer together.
______________________________
Once it was rotated counterclockwise, or toward the spine of the book, it seemed to have a fairly consistant progression of sounds.
___________________________
When it was rotated again, or facing the bottom of the book, the sounds got further apart.
___________________________
When rotated again, or facing the side of the book where it opens, the pearl once again made fairly consistent beats on the pendulum.
** Your description of how you oriented the bracket on the tilted surface to obtain a steady rhythm: **
I would orient the bracket facing one of the sides, for example the side (or the fourth rotation experienced) because it is not one extreme or the other. It is in the middle. It does not let the pearl hang closer or farther from the pendulum. It stays in the same position.
** Your report of 8 time intervals between release and the second 'hit': **
2.344,.453
2.767,.406
3.078,.391
3.0469,.484
2,.469
2.141,.484
2.094,.438
2.156,.516
The first number in the interval is when I simultaneously clicked the timer program and released the 'pearl.' The second number is when I clicked the timer program because the 'pearl' struck the bracket the second time.
** Your report of 4 trials timing alternate hits starting with the second 'hit': **
.625,.625.625,.703
.531,.688,.641,.703
.563,.641,.625,.656
.594,.594,.672,.813
.688,.703,.688,.625
.594,.641,.656,.609
.641,.656,.625
.672,.609,.672,.656,.766
These numbers are the numbers I found by clicking on the timer probgram every two hits of the 'pearl' on the bracket.
** The length of your pendulum in cm (you might have reported length in mm; the request in your instructions might have been ambiguous): **
8.8mm
** Your time intervals for alternate 'hits', starting from release until the pendulum stops swinging: **
.454,.625,.646
** Your description of the pendulum's motion from release to the 2d hit: **
When the 'pearl' was released from the extreme point, it first struck the bracket, or equilibrium, then returned close to the extreme point again. Because there was a loss of energy, the 'pearl' will never gain back that full potential that it started with.
** Your description of the pendulum's motion from the 2d hit to 4th hit: **
The motion between the first hit and second hit was different than the motion between the release and first hit because it was a longer time that had elapsed. When released, it only had to go half of the way before it struck the bracket, whereas between the first and second hit, it had to make one full cycle.
** 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: **
The motion between release and the second hit and the motion between the second and fourth hit should have been similar, but possibly the first was over a slightly longer period of time because it made a full cycle and a half as opposed to one full cycle.
** 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: **
The motion between the second and fourth hit was slightly faster than the motion between the fourth and sixth hits in my experiment.
** Your conjecture as to why a clear difference occurs in some intervals vs. others: **
The first time interval should be shortest because as the experiment goes on, the 'pearl' loses momentum.
** What evidence is there that subsequent intervals increase, decrease or remain the same: **
The time intervals in my case tended to decrease over time because the momentum continued to lose strength.
If the pendulum was set up as instructed, so that they rhythm of the ‘beats’ was even, the time intervals would not have changed significantly. The decreasing distance tends to decrease the time required, while the decreasing velocity would tend to increase the time required. It turns out that the two factors balance one another.
** What evidence is there that the time between 'hits' is independent of the amplitude of the swing? **
This experiment shows that these two things go hand and hand. Both the length and how far it swings affects the pendulum.
** **
2 Hours
** **
It took me a few minutes, however, to locate the problem with the timer program.
Be sure to see my note and let me know if you don’t understand.