Phy 231
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' **
It seems to me that it hits faster at first and then at a constant rate before stopping abruptly.
However, I'm using a round pendant instead of the pearl because I couldn't find it in the lab packet (I have the bracket and the magnets and the thread and everything, but not the pearl). Since the pendant has a few jewels on it, that could have affected the surface area and the angle that it hit, impeding the rebound.
I think the motion was supposed to be constant even if my results don't show this.
** Your description of the rhythm of the pendulum when tilted 'forward' **
Note: I changed the pearl to one of the hydrogens in my chemistry set since it already had a hole through the middle and a smooth surface area (the prior trial seemed very close to constant, but it may have been slowing just a tiny bit).
The rhythm gets faster on this trial. The dinging noise came in far shorter intervals.
** Your description of the process used to keep the rhythm steady and the results you observed: **
I had to keep tilting it backward (more level) slightly whenever it couldn't reach the bracket, and then the rhythm stayed fairly steady. The pendulum hit the bracket about 12 or 13 times.
** Your description of what happened on the tilted surface (textbook and domino), rotating the system 45 degrees at a time: **
I began with the bracket/pendulum pointed away from the middle of the book and rotated 45 degrees counterclockwise each time.
9 times, fairly constant
10 times, fairly constant
13 times, fairly constant
14 times, shorter intervals as time increases
12 times, much shorter intervals as time increases
12 times, shorter intervals
11 times, fairly constant
10 times, fairly constant
** Your description of how you oriented the bracket on the tilted surface to obtain a steady rhythm: **
I would angle it tilted forward just slightly.
** Your report of 8 time intervals between release and the second 'hit': **
.391
.359
.344
.328
.328
.391
.344
.328
This is how long the ball takes from point of release to its second hit. I just clicked the timer simultaneously and clicked again when it hit the second time.
** Your report of 4 trials timing alternate hits starting with the second 'hit': **
.266, .359, .563, .469, .539, .703, .695
These are the intervals between every 2 hits. I guess I might have had more intervals because my ball is smaller? Or maybe I held it higher or because it isn't as long as it probably could have been.
** The length of your pendulum in cm (you might have reported length in mm; the request in your instructions might have been ambiguous): **
5.7 cm
** Your time intervals for alternate 'hits', starting from release until the pendulum stops swinging: **
.266, .359, .563, .469, .539, .703, .695
** Your description of the pendulum's motion from release to the 2d hit: **
It would be 1/4 of a cycle or 1 interval.
** Your description of the pendulum's motion from the 2d hit to 4th hit: **
It would be 1/2 of a cycle, since a cycle involves 4 quarters (from extreme to equilibrium to other extreme to equilibrium back to extreme). The second hit occurs after 3 of these 1/4th cycles (from extreme to equilibrium back to extreme to equilibrium) from rest and 2 of these 1/4th cycles (intervals) from the time that the first hit occurred.
It differs from the interval between release and first hit because it has go back to extreme before returning to equilibrium, making it 2 intervals instead of one (this interval starts at equilibrium instead of extreme).
** 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: **
It would be 3/4 of a cycle. The second hit occurs after 3 of the 1/4th intervals (from extreme to equilibrium back to extreme to equilibrium).
I guess it would differ from the motion between second hit and fourth hit because the interval begins at the extreme instead of the equilibrium (so the motion between the second and fourth hit would be 1 cycle or 4 intervals instead of 3).
** 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: **
Well, they'd both be 4 intervals or 1 cycle, although I supposed you'd have to take into account that the extreme point is going to be at a shorter distance from the equilibrium point between the fourth and sixth hit.
** Your conjecture as to why a clear difference occurs in some intervals vs. others: **
Well, it has 1/4 less the distance to travel, and it's also going faster.
** What evidence is there that subsequent intervals increase, decrease or remain the same: **
I'd expect subsequent time intervals to increase judging from my data.
** What evidence is there that the time between 'hits' is independent of the amplitude of the swing? **
I don't entirely understand the question. Its length of swing is independent of its length of swing?
time between 'hits' is not the same thing as 'length of swing'.
Hint: You set the thing up so the rhythm would remain steady.
I guess the experiment supports the hypothesis that no matter where you start the release and therefore the original length of swing, the relationship between intervals will be relatively similar since there's no real way of measuring the point of release and the data was pretty similar earlier on (the 8 trials), although that could also be partly due to the large possibility of human error in gauging times that small.
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1.5 hr
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&#Good responses. Let me know if you have questions. &#