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' **
The rhythm speeds up at an increasing rate with the bracket tilted back. It starts of somewhat slowly but then gets much faster towards the end.
** Your description of the rhythm of the pendulum when tilted 'forward' **
The rhythm seems to remain constant until the very end. The last few taps seem to slow down, but the majority of the bounces are the same rhythm.
** Your description of the process used to keep the rhythm steady and the results you observed: **
I used a ruler under the back end of the bracket, and adjusted its position forward and backward until the bouncing was as even as possible. The rhythm seemed pretty steady. I counted between 19-22 bounces.
** Your description of what happened on the tilted surface (textbook and domino), rotating the system 45 degrees at a time: **
The experiment is performed using the Giancoli textbook, the pearl pendulum and two dominos. I placed the dominos under the book (one lined up exactly with each corner with the long side of each domino lined up exactly with the long edge of the book) to create a ramp. Place the bracket such that the pearl pendulum is facing the bottom edge of the ramp. Raise and release the pendulum. Note the bounce rate of the pendulum, particularly whether it is increasing or decreasing. My results are below:
Facing the bottom of the ramp is 0 degrees rotation. Each interval of rotation is counter clockwise by 45 degrees.
0 degrees - fairly even rate, decreasing slightly toward the end
45 degrees - fairly even rate, decreasing slightly faster toward the end
90 degrees - decreasing slowly throughout, decreasing slightly faster toward the end
135 degrees - decreasing throughout, decreasing fast toward the end
180 degrees - decreasing quickly throughout, decreasing very fast toward the end
225 degrees - decreasing throughout, decreasing fast toward the end
270 degrees - decreasing slowly throughout, decreasing slightly faster toward the end
315 degrees - fairly even rate, decreasing slightly faster toward the end
** Your description of how you oriented the bracket on the tilted surface to obtain a steady rhythm: **
I think that the most regular beat is with the pendulum facing straight toward the bottom of the book (the 0 degree position). I believe that my pendulum is oriented a little more toward the leaning back position.
** Your report of 8 time intervals between release and the second 'hit': **
.344 s
.293 s
.375 s
.297 s
.438 s
.387 s
.547 s
.375 s
These numbers are the trials timing the period between the release and the second bounce of the pearl pendulum when it is sitting on top of the physics book propped up on dominos and facing the bottom of the ramp as described previously.
** Your report of 4 trials timing alternate hits starting with the second 'hit': **
.434, .390, .219, .637, .578, .578, .653
.559, .500, .609, .605, .563, .715
.406, .574, .609, .640, .590, .625
.531, .469, .621, .578, .637, .594, .609
These results are the intervals between two bounces. One trial per line, over four trials. They were obtained by licking the timer program as close as possible to each second bounce of the pendulum. According to my results it looks like I picked a position where the pendulum is slowing down slightly during each set of bounces.
** The length of your pendulum in cm (you might have reported length in mm; the request in your instructions might have been ambiguous): **
9.8 cm
** Your time intervals for alternate 'hits', starting from release until the pendulum stops swinging: **
.483, .483, .515
** Your description of the pendulum's motion from release to the 2d hit: **
When the pendulum is released it leaves its most extreme point. When it is near its equilibrium point it strikes the bracket (the first hit). After the hit it rebounds and moves toward the most extreme point, but doesn't quite reach this point.
** Your description of the pendulum's motion from the 2d hit to 4th hit: **
Between the first hit and the second hit the pendulum rebounds off the bracket, approaches the extreme point, and then falls back to the bracket. This is the same motion overall as before, but with slightly less energy. The bounces don't go quite as high.
** 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 release to 2nd hit motion is a slightly greater magnitude than the 2nd hit to 4th hit motion. The average times between these two time periods came out to be exactly the same in my results.
** 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 release to 2nd hit motion is a slightly lower magnitude than the 4th hit to 6th hit motion. The average times between 4-6 were slower than the averages for 2-4 in my results.
** Your conjecture as to why a clear difference occurs in some intervals vs. others: **
The first interval is only covering 3 half motions of the pendulum vs. 4 half motions of the pendulum for the subsequent intervals.
Good. More specifically it is 3 quarter-cycles vs. 4 quarter-cycles.
** What evidence is there that subsequent intervals increase, decrease or remain the same: **
Since I left my pendulum facing the absolute bottom of the ramp, it seemed to slow a bit, but most of the intervals were very close to being the same.
** What evidence is there that the time between 'hits' is independent of the amplitude of the swing? **
I think that this hypothesis is supported by the data gathered. The pendulum can either be placed such that gravity is speeding it up or slowing it down, but it is also possible to place it in a gravity neutral position. In this position the period of the pendulum seems to be mostly independent of the magnitude of the swing.
** **
1.5 hrs
** **
I rarely get to work on any of the assignments uninterrupted. There always seem to be a child, wife, animal, or work emergency that needs attention :-) So, my times are probably well longer than the averages.
It is difficult to work efficiently through interruptions.
In any case the quality of your work is excellent. See my notes.