Phy 121
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The bracket being in its normal position resting on the table, makes the bead bounce off it about 5-7 times per release. The bounces or rhythm gets closer together until it stops. The rhythm seems to get faster, or the bounces get closer together before it stops. #$&* If the bracket is tilted forward a bit, as shown in the figure below, the pearl will naturally hang away from the bracket. Tilt the bracket forward a little bit (not as much as shown in the figure, but enough that the pearl definitely hangs away from the bracket). Keep the bracket stationary and release the pendulum. Note whether the pearl strikes the bracket more and more frequently or less and less frequently with each bounce. Again listen to the rhythm of the sounds made by the ball striking the bracket. Do the sounds get closer together or further apart, or does the rhythm remain steady? I.e., does the rhythm get faster or slower, or does it remain constant? Repeat a few times if necessary until you are sure of your answer. Insert your answer into the box below, and give a good description of what you heard.your response &&&&&&&&&&&&&&&&&&
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I placed a domino beneath the far end of the bracket to make the pearl hang away from the bracket just a little. The sounds get closer together, but it definitely takes longer per swing for the pearl to strike the bracket, and the time between bounces is also longer. #$&* If the bracket is placed on a perfectly level surface, the pearl will hang straight down, just barely touching the bracket. However most surfaces on which you might place the bracket aren't perfectly level. Place the bracket on a smooth surface and if necessary tilt it a bit by placing a shim (for a shim you could for example use a thin coin, though on most surfaces you wouldn't need anything this thick; for a thinner shim you could use a tightly folded piece of paper) beneath one end or the other, adjusting the position and/or the thickness of the shim until the hanging pearl just barely touches the bracket. Pull the pearl back then release it. If the rhythm of the pearl bouncing off the bracket speeds up or slows down, adjust the level of the bracket, either tilting it a bit forward or a bit backward, until the rhythm becomes steady. Describe the process you used to make the rhythm steady, and describe just how steady the rhythm was, and how many times the pendulum hit the bracket..your response &&&&&&&&&&&&&&&&&&
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I made the rhythm steady by placing a piece of paper folded under the far end of the bracket. The piece of paper was folded twice (meaning it was basically four papers thick) until the rhythm got steady. #$&* On a reasonably level surface, place one domino under each of the top left and right corners of your closed textbook, with the front cover upward. Place the bracket pendulum on the middle of the book, with the base of the bracket parallel to one of the sides of the book. Release the pendulum and observe whether the sounds get further apart or closer together. Note the orientation of the bracket and whether the sounds get further apart or closer together. Now rotate the base of the bracket 45 degrees counterclockwise and repeat, being sure to note the orientation of the bracket and the progression of the sounds. Rotate another 45 degrees and repeat. Continue until you have rotated the bracket back to its original position. Report your results in such a way that another student could read them and duplicate your experiment exactly. Try to report neither more nor less information than necessary to accomplish this goal. Use a new line to report the results of each new rotation.your response &&&&&&&&&&&&&&&&&&
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When the corner part of the bracket was raised by the dominos in the book, the rhythm seemed the most changing, Rotating the bracket so that the corner part is facing the bottom or the top of the book seemed to get equal results, but the rhythm still was not all that steady. Orienting the bracket so that the corner faces the spine of the book and the tail of the bracket is lifted by the dominos, seemed to work best. Here the bead just rest just slightly away from the bracket. This definitely resulted in the steadiest rhythm, although al rhythms get faster and faster until they stop. #$&* Describe how you would orient the bracket to obtain the most regular 'beat' of the pendulum.your response &&&&&&&&&&&&&&&&&&
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The orientation for the most beats, and the most regular rhythm, seems to be the same. Raiding the back of the bracket to where the bead is resting just slightly away from the bracket seems to work best. #$&* Orient the bracket in this position and start the TIMER program. Adjust the pendulum to the maximum length at which it will still bounce regularly. Practice the following procedure for a few minutes: Pull the pendulum back, ready to release it, and place your finger on the button of your mouse. Have the mouse cursor over the Click to Time Event button. Concentrate on releasing the pendulum at the same instant you click the mouse, and release both. Do this until you are sure you are consistently releasing the pendulum and clicking the mouse at the same time. Now you will repeat the same procedure, but you will time both the instant of release and the instant at which the pendulum 'hits' the bracket the second time. The order of events will be: click and release the pendulum simultaneously the pendulum will strike the bracket but you won't click the pendulum will strike the bracket a second time and you will click at the same instant We don't attempt to time the first 'hit', which occurs too soon after release for most people to time it accurately. Practice until you can release the pendulum with one mouse click, then click again at the same instant as the second strike of the pendulum. When you think you can conduct an accurate timing, initialize the timer and do it for real. Do a series of 8 trials, and record the 8 time intervals below, one interval to each line. You may round the time intervals to the nearest .001 second. Starting in the 9th line, briefly describe what your numbers mean and how they were obtained.your response &&&&&&&&&&&&&&&&&&
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1 .40625 2 .578125 3 .546875 4 .4375 5 .578125 6 .578125 7 .46875 8 .578125 These results were obtained as instructed above. The bracket was oriented with the back slightly raised so the bead rest slightly away from the face at equilibrium. The same time interval appeared 4 times out of 8 trials, meaning the timing was fairly accurate and precise. #$&* Finally, you will repeat once more, but you will time every second 'hit' until the pendulum stops swinging. That is, you will release, time the second 'hit', then time the fourth, the sixth, etc.. Practice until you think you are timing the events accurately, then do four trials. Report your time intervals for each trial on a separate line, with commas between the intervals. For example look at the format shown below: .925, .887, .938, .911 .925, .879, .941 etc. In the example just given, the second trial only observed 3 intervals, while the first observed 4. This is possible. Just report what happens in the space below. Then on a new line give a brief description of what your results mean and how they were obtained.your response &&&&&&&&&&&&&&&&&&
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.5, .5625, .484375, .3796875 .5, .828125, .703125 .359375, .5, .71875, .578125 .703125, .671875, .65625 .515625, 1.03125, .78125 .5625, .515625, .71875, .546875 The pendulum is taking different time lengths from what I had assumed. It seams the longest is the second swing, while each consecutive swing gets shorter and shorter until it stops. #$&* Now measure the length of the pendulum. (For the two-pearl system the length is measured from the bottom of the 'fixed' pearl (the one glued to the top of the bracket) to the middle of the 'swinging' pearl. For the system which uses a bolt and magnet at the top instead of the pearl, you would measure from the bottom of the bolt to the center of the pearl). Using a ruler marked in centimeters, you should be able to find this length to within the nearest millimeter. What is the length of the pendulum?your response &&&&&&&&&&&&&&&&&&
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10.7 cm #$&* If you have timed these events accurately, you will see clearly that the time from release to the second 'hit' appears to be different than the time between the second 'hit' and the fourth 'hit'. On the average, how much time elapses between release and the second 'hit' of the pendulum, how much time elapses between the second and fourth 'hit' and how much time elapses between the fourth and sixth 'hit'? Report your results as three numbers separated by commas, e.g., .63, .97, .94your response &&&&&&&&&&&&&&&&&&
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.18, .13, .02 #$&* A full cycle of a free pendulum is from extreme point to equilibrium to opposite extreme point then back to equilibrium and finally back to the original extreme point (or almost to the original extreme point, since the pendulum is losing energy as it swings).. The pearl pendulum is released from an 'extreme point' and strikes the bracket at its equilibrium point, so it doesn't get to the opposite extreme point. If an interval consists of motion from extreme point to equilibrium, or from equilibrium to extreme point, how many intervals occur between release and the first 'hit'?your response &&&&&&&&&&&&&&&&&&
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From one extreme point to equilibrium, then the pendulum competed one cycle fro release to the first hit. #$&* How many intervals, as the word was described above, occur between the first 'hit' and the second 'hit'? Explain how your description differs from that of the motion between release and the first 'hit'.your response &&&&&&&&&&&&&&&&&&
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Two, falling from extreme point to fist hit is one, but returning to the point and then bacl to the second hit, results in 2 cycles. #$&* How many intervals occur between release and the second 'hit', and how does this differ from the motion between the second 'hit' and the fourth 'hit'?your response &&&&&&&&&&&&&&&&&&
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Intervals between first hit and second hit = 2. Intervals between second hit and fourth hit, is 4. So there are twice as many intervals, although each interval is getting shorter. There are two motions between the two hits, two back-and-forth motions. #$&* How many intervals occur between the second 'hit' and the fourth 'hit', and how does this differ from a similar description of the motion between the fourth 'hit' and the sixth 'hit'?your response &&&&&&&&&&&&&&&&&&
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Intervals = 4. The fourth hit and sixth hit have two motions in between them, the midpoint of which is the fifth hit. #$&* Why would we expect that the time interval between release to 2d 'hit' should be shorter than the subsequent timed intervals (2d to 4th, 4th to 6th, etc.)?your response &&&&&&&&&&&&&&&&&&
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The pendulum is losing energy. From release to the second hit, is the most ebergy it has, meaning it travels the fastest. #$&* Would we expect additional subsequent time intervals to increase, decrease or stay the same?your response &&&&&&&&&&&&&&&&&&
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Additional time intervals would decrease, because the distance the pendulum travels from the bracket after each hit is decreasing, meaning the time it takes to return for another hit is also decreasing. #$&* What evidence does this experiment provide for or against the hypothesis that the length of a pendulum's swing depends only on its length, and is independent of how far it actually swings?your response &&&&&&&&&&&&&&&&&&
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The length of the pendulum swing depends not only on, its length, but also the amount of energy behind the swing. A longer pendulum will swing less if it is only nudged, as a shorter pendulum will swing further if it is brought to one extreme before being released. #$&* Your instructor is trying to gauge the typical time spent by students on these experiments. Please answer the following question as accurately as you can, understanding that your answer will be used only for the stated purpose and has no bearing on your grades: Approximately how long did it take you to complete this experiment?your response &&&&&&&&&&&&&&&&&&
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About 1.5 hours