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: **
** Your description of the rhythm of the pendulum when tilted 'back' **
The sounds get closer together and the rhythm gets faster.
** Your description of the rhythm of the pendulum when tilted 'forward' **
The sound gets further apart.
** Your description of the process used to keep the rhythm steady and the results you observed: **
My bracket had a washer and a bolt glued to the bottom of it, so when it was placed on a level surface the bead would hang so that there was a little space between the bracket and it. The rhythm of the bead hitting the bracket is very steady and the bead hit the bracket about 6 times.
** Your description of what happened on the tilted surface (textbook and domino), rotating the system 45 degrees at a time: **
In the first part, I place the bracket parallel to the long sides of the book with the side that the pearl was on facing the top of the book. When I released the pearl while in this position the rhythm increased. The sounds were getting closer together.
With the first 45 degree counterclockwise rotation, the pearl side of the bracket is now pointed toward the top corner of the book on the spine side. When I release the pearl the sound was a steady rhythm.
In rotating the bracket another 45 degrees counterclockwise, the pearl is now facing the spine side of the book. When released the pearl had a steady rhythm.
In the next rotation of 45 degrees counterclockwise, the pearl is now facing the bottom corner of the spine side of the book. When the pearl is released from this position the sound appears to be getting farther apart.
In the next rotation of 45 degrees counterclockwise, the pearl is now facing the bottom edge of the book. When the pearl is released from this position the sound is defiantly getting farther apart. It was a little harder to detect in the previous poisiton, however, now it is very distinctive.
In this rotation of 45 degrees counterclockwise, the pearl is now facing the bottom corner of the open side of the book. When the pearl is released from this position the sound appears to be getting farther apart.
In this rotation of 45 degrees counterclockwise, the pearl is now facing the center of the opened side of the book. When released from this position the rhythm is steady again.
In this rotation of 45 degrees counterclockwise, the pearl is now facing the top corner of the opened side of the book. When released the pearl has an increased rhythm, the sound is getting closer together.
** Your description of how you oriented the bracket on the tilted surface to obtain a steady rhythm: **
When the bracket was facing the spine and opened sides of the book, it had the most steady rhythm.
** Your report of 8 time intervals between release and the second 'hit': **
Trial 1 .453
Trail 2 .406
Trail 3 .348
Trail 4 .423
Trail 5 .323
Trail 6 .418
Trail 7 .371
Trail 8 .406
I obtained these numbers by click the timer first when the bead was released and then again when the bead hit the bracket the second time. I believe waiting for the second hit gives you the period of that cycle of the pendulum swing.
** Your report of 4 trials timing alternate hits starting with the second 'hit': **
Trail 1 .547, .422, .605
Trail 2 .578, .5, .465
Trail 3 .609, .547, .531, 543
Trail 4 .563, .563, .652, .351
Trail 5 .453, .465, .516, .641
Trail 6 .578, .5, .625, .543
Trail 7 .453, .527, .672, .531
Trail 8 .578, .656, .699
These results were obtained by setting the bracket up with the pearl side facing the center of the spine side the book. The reason it was measured this way was inorder to time a full cycle for the pendulum.
** The length of your pendulum in cm (you might have reported length in mm; the request in your instructions might have been ambiguous): **
6 cm.
** Your time intervals for alternate 'hits', starting from release until the pendulum stops swinging: **
.545, .523, .596
** Your description of the pendulum's motion from release to the 2d hit: **
Between release and the first hit is only one third of the cycle, or one interval.
** Your description of the pendulum's motion from the 2d hit to 4th hit: **
Two intervals occur from the first hit to the second hit. This is different from the previous question, because the pearl goes from equilibrium to extreme point, back to equilibrium.
** 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: **
Three intervals occur from release to the second hit. This is different from the motion because there are 4 intervals between the second hit and fourth hit.
** 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: **
There are four intervals between the second and fourth hit and four between the fourth and sixth hits. So there is no real difference in the number of intervals.
** Your conjecture as to why a clear difference occurs in some intervals vs. others: **
Because it has one less swing involved in it.
** What evidence is there that subsequent intervals increase, decrease or remain the same: **
I would expect them to decrease as the pendulum losses energy.
** What evidence is there that the time between 'hits' is independent of the amplitude of the swing? **
With each swing of the pendulum, it is not going to go to the full length of the string each time, that is why we measure the different swings.
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50 minutes
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Very well done.