#$&* Phy 201
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The sound of the pendulum hitting the bracket when the pendulum is released get clower together as time elapses. #$&* 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 sounds get further apart as time elapses and eventually the pendulum keeps moving but does not hit the bracket. #$&* If the bracket is placed on a perfectly level surface, the pearl will hang straight down, just barely touching the bracket. However most surfaces on which you might place the bracket aren't perfectly level. Place the bracket on a smooth surface and if necessary tilt it a bit by placing a shim (for a shim you could for example use a thin coin, though on most surfaces you wouldn't need anything this thick; for a thinner shim you could use a tightly folded piece of paper) beneath one end or the other, adjusting the position and/or the thickness of the shim until the hanging pearl just barely touches the bracket. Pull the pearl back then release it. If the rhythm of the pearl bouncing off the bracket speeds up or slows down, adjust the level of the bracket, either tilting it a bit forward or a bit backward, until the rhythm becomes steady. Describe the process you used to make the rhythm steady, and describe just how steady the rhythm was, and how many times the pendulum hit the bracket..your response &&&&&&&&&&&&&&&&&&
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When released on a level surface, the pendulum hitting the bracket speeds up. In order for the sound to be consistant, I had to tilt the bracket forward only slightly so that the pendulum hung slightyly away from the bracket, the pendulum hit the bracket in a consistant motion 9 times before the motion did not reach the bracket. #$&* 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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With the bracket in the starting postion above, the sounds grew further apart as time elapsed. When rotated to the right 45 degrees, the sounds were relitively constant. When rotated in the same direction again, the sounds grew closer together. When rotated another 45 degrees in the same direction, the sounds were, again, relitiveily constant. #$&* Describe how you would orient the bracket to obtain the most regular 'beat' of the pendulum.your response &&&&&&&&&&&&&&&&&&
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I would orient the braket so that it were running parellel with the top and bottom of the book. #$&* 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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.405 .515 .421 .499 .546 .640 .484 .437 these numbers were obtained by using the directions above and clikcing the TIMER program at release and second hit. That means, this is the time it takes the pendulum to hit the bracket a second time after release. #$&* Finally, you will repeat once more, but you will time every second 'hit' until the pendulum stops swinging. That is, you will release, time the second 'hit', then time the fourth, the sixth, etc.. Practice until you think you are timing the events accurately, then do four trials. Report your time intervals for each trial on a separate line, with commas between the intervals. For example look at the format shown below: .925, .887, .938, .911 .925, .879, .941 etc. In the example just given, the second trial only observed 3 intervals, while the first observed 4. This is possible. Just report what happens in the space below. Then on a new line give a brief description of what your results mean and how they were obtained.your response &&&&&&&&&&&&&&&&&&
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.375, .374, .328 .390, .374, .297 .296, .406, .343 .374, .499, .422 These results were found by clikcing the TIMER program every second hit on the bracket. These show me that the pendulum takes between 3 and 4 seconds to hit the bracket every second time #$&* 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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12.5 cm #$&* If you have timed these events accurately, you will see clearly that the time from release to the second 'hit' appears to be different than the time between the second 'hit' and the fourth 'hit'. On the average, •how much time elapses between release and the second 'hit' of the pendulum, •how much time elapses between the second and fourth 'hit' and •how much time elapses between the fourth and sixth 'hit'? Report your results as three numbers separated by commas, e.g., .63, .97, .94your response &&&&&&&&&&&&&&&&&&
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.36, .41, .46 #$&* 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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1 interval #$&* How many intervals, as the word was described above, occur between the first 'hit' and the second 'hit'? Explain how your description differs from that of the motion between release and the first 'hit'.your response &&&&&&&&&&&&&&&&&&
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2. The release to the first hit is only one because it is going from one extreme to equilibrium #$&* 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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3. The motion from the second to fourth hit would be 4 intervals. #$&* How many intervals occur between the second 'hit' and the fourth 'hit', and how does this differ from a similar description of the motion between the fourth 'hit' and the sixth 'hit'?your response &&&&&&&&&&&&&&&&&&
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4.The intervals would be the same from the 4th to 6th hit, but the time interval would be longer. #$&* 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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The time interval would be shorter because the pendulum is losing energy and therefore the extreme position is much closer. #$&* Would we expect additional subsequent time intervals to increase, decrease or stay the same?your response &&&&&&&&&&&&&&&&&&
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The would continue to decrease until the pendulum stops. #$&* 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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This shows that the length of the swing has the greatest effecct on the time interval. #$&* Your instructor is trying to gauge the typical time spent by students on these experiments. Please answer the following question as accurately as you can, understanding that your answer will be used only for the stated purpose and has no bearing on your grades: •Approximately how long did it take you to complete this experiment?your response &&&&&&&&&&&&&&&&&&
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About 45 minutes #$&*