Phy 201
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The rhythm gets faster and the sound gets closer together. The pearl hits the bracket a few times then the rhythm gets faster and the sound gets closer together until it stops all together. #$&* If the bracket is tilted forward a bit, as shown in the figure below, the pearl will naturally hang away from the bracket. Tilt the bracket forward a little bit (not as much as shown in the figure, but enough that the pearl definitely hangs away from the bracket). Keep the bracket stationary and release the pendulum. Note whether the pearl strikes the bracket more and more frequently or less and less frequently with each bounce. Again listen to the rhythm of the sounds made by the ball striking the bracket. Do the sounds get closer together or further apart, or does the rhythm remain steady? I.e., does the rhythm get faster or slower, or does it remain constant? Repeat a few times if necessary until you are sure of your answer. Insert your answer into the box below, and give a good description of what you heard.your response &&&&&&&&&&&&&&&&&&
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The sound gets farther apart and the rhythm gets slower. The pearl strikes the bracket less and less frequently with each bounce. #$&* 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 taking a folding a piece of paper and placing it under the bracket. The rhythm was very steady with the pearl hitting the bracket 15 times. #$&* 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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The front of the bracket with the pearl starts off parallel to the bottom side of the book. The sounds got farther away. Rotating it 45 degrees counterclockwise the pearl is facing the right side of the book and the sounds got farther away. Another 45 degrees the pearl is parallel to the right side of the book and the sounds got farther away. 45 more degrees and the pearl is facing the top of the right side of the book and the sounds closer together. 45 degrees and the pearl is parallel to the top side of the book with the sounds got closer together. 45 degrees the pearl is facing the top left side of the book and the sounds got closer together. 45 degrees and the pearl is parallel to the left side of the book and the sounds got farther away. 45 degrees and the pearl is facing the lower left side of the book and the sounds got farther away. 45 degrees and the pearl is back to being parallel to the bottom side of the book with the sounds farther away. #$&* Describe how you would orient the bracket to obtain the most regular 'beat' of the pendulum.your response &&&&&&&&&&&&&&&&&&
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I would orient the bracket so the pearl is parallel to the bottom side of the book to get the most regular beat of the pendulum. #$&* Orient the bracket in this position and start the TIMER program. Adjust the pendulum to the maximum length at which it will still bounce regularly. Practice the following procedure for a few minutes: Pull the pendulum back, ready to release it, and place your finger on the button of your mouse. Have the mouse cursor over the Click to Time Event button. Concentrate on releasing the pendulum at the same instant you click the mouse, and release both. Do this until you are sure you are consistently releasing the pendulum and clicking the mouse at the same time. Now you will repeat the same procedure, but you will time both the instant of release and the instant at which the pendulum 'hits' the bracket the second time. The order of events will be: click and release the pendulum simultaneously the pendulum will strike the bracket but you won't click the pendulum will strike the bracket a second time and you will click at the same instant We don't attempt to time the first 'hit', which occurs too soon after release for most people to time it accurately. Practice until you can release the pendulum with one mouse click, then click again at the same instant as the second strike of the pendulum. When you think you can conduct an accurate timing, initialize the timer and do it for real. Do a series of 8 trials, and record the 8 time intervals below, one interval to each line. You may round the time intervals to the nearest .001 second. Starting in the 9th line, briefly describe what your numbers mean and how they were obtained.your response &&&&&&&&&&&&&&&&&&
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.375 second .359 second .359 second .406 second .484 second .516 second .578 second .593 second The numbers were obtained from the TIMER program I started it off as I was letting the pendulum go and clicked the second hit and every hit after that for 8 trials. The numbers show that the hits got farther apart as the pendulum kept swinging. #$&* 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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.578, .578, .609, .578 .578, .421, .515, .562 .531, .343, .421, .531 .484, .453, .593, .546 #$&* Now measure the length of the pendulum. (For the two-pearl system the length is measured from the bottom of the 'fixed' pearl (the one glued to the top of the bracket) to the middle of the 'swinging' pearl. For the system which uses a bolt and magnet at the top instead of the pearl, you would measure from the bottom of the bolt to the center of the pearl). Using a ruler marked in centimeters, you should be able to find this length to within the nearest millimeter. What is the length of the pendulum?your response &&&&&&&&&&&&&&&&&&
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9.82 cm #$&* 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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.54, .094, .086 #$&* A full cycle of a free pendulum is from extreme point to equilibrium to opposite extreme point then back to equilibrium and finally back to the original extreme point (or almost to the original extreme point, since the pendulum is losing energy as it swings).. The pearl pendulum is released from an 'extreme point' and strikes the bracket at its equilibrium point, so it doesn't get to the opposite extreme point. It an interval consists of motion from extreme point to equilibrium, or from equilibrium to extreme point, how many intervals occur between release and the first 'hit'?your response &&&&&&&&&&&&&&&&&&
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There are two intervals between release and the first hit. #$&* 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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There are 3 intervals between the first hit and the second. This differs from the release and first hit because from release it goes directly to the first hit. However from the first hit it goes to the extreme and back again so there are 3 intervals and the pendulum loses momentum. #$&* How many intervals occur between release and the second 'hit', and how does this differ from the motion between the second 'hit' and the fourth 'hit'?your response &&&&&&&&&&&&&&&&&&
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There are four intervals between the release and second hit and are shorter. This differs from the second and fourth hit because it has one less interval and they are longer. #$&* 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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5 intervals occur between the second and fourth hit. The fourth and sixth hits also have 5 intervals but these intervals are slower and longer. #$&* Why would we expect that the time interval between release to 2d 'hit' should be shorter than the subsequent timed intervals (2d to 4th, 4th to 6th, etc.)?your response &&&&&&&&&&&&&&&&&&
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Because as the pendulum moves and the pearl hits the bracket it loses energy and momentum so the pendulum slows down and the intervals are longer in the 2nd to 6th etc hits. When the pendulum first goes it has more energy so the hits are shorter. #$&* Would we expect additional subsequent time intervals to increase, decrease or stay the same?your response &&&&&&&&&&&&&&&&&&
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We would expect addition time intervals to decrease. #$&* What evidence does this experiment provide for or against the hypothesis that the length of a pendulum's swing depends only on its length, and is independent of how far it actually swings?your response &&&&&&&&&&&&&&&&&&
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The length of the intervals between hits shows evidence against the hypothesis that the length of a pendulums swing depends only on its length, and is independent of how far it actually swings. This is because the length of a pendulums swing is dependent on the length and how far is swings from extreme point. The time the intervals take show this. #$&* 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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1.5 hours #$&*