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Phy 231
Your 'cq_1_00.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
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The problem:
You don't have to actually do so, but it should be clear that if you wished to do so, you could take several observations of positions and clock times. The main point here is to think about how you would use that information if you did go to the trouble of collecting it. However, most students do not answer these questions in terms of position and clock time information. Some students do not pause the video as instructed. To be sure you are thinking in terms of positions and clock times, please take a minute to do the following, which should not take you more than a couple of minutes:
• Pick one of the videos, and write down the position and clock time of one of the objects, as best you can determine them, in each of three different frames. The three frames should all depict the same 'roll' down the ramp, i.e. the same video clip, at three different clock times. They should not include information from two or more different video clips.
• For each of the three readings, simply write down the clock time as it appears on the computer screen, and the position of the object along the meter stick. You can choose either object (i.e., either the pendulum or the roll of tape), but use the same object for all three measurements. Do not go to a lot of trouble to estimate the position with great accuracy. Just make the best estimates you can in a couple of minutes.
Which object did you choose and what were the three positions and the three clock times?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
I chose the tape role:
59.359, 3 inches
59.687, 12 inches
60.015, 22 inches
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In the following you don't have to actually do calculations with your actual data. Simply explain how you would use data of this nature if you had a series of several position vs. clock time observations:
• If you did use observations of positions and clock times from this video, how accurately do you think you could determine the positions, and how accurately do you think you would know the clock times? Give a reasonable numerical answer to this question (e.g., positions within 1 meter, within 2 centimeters, within 3 inches, etc; clock times within 3 seconds, or within .002 seconds, or within .4 seconds, etc.). You should include an explanations of the basis for your estimate: Why did you make the estimate you did?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
Positions within a quarter inch and clock times within .01 seconds. I based the positions on what I could see in the video and the associated blurriness. I based on the clock times on the times I could see on the computer in the video and took off one significant digit, assuming that the last significant digit on the computer is rounded.
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• How can you use observations of position and clock time to determine whether the tape rolling along an incline is speeding up or slowing down?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
Determine the position of the tape compared to a series of clock times, with a constant interval between the clock times. If the difference in the position of the tape increases while the difference in the clock times remains constant, then the tape is speeding up.
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• How can you use observations of position and clock time to determine whether the swinging pendulum is speeding up or slowing down?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
Same answer: Determine the position of the pendulum compared to a series of clock times, with a constant interval between the clock times. If the difference in the position of the pendulum increases while the difference in the clock times remains constant, then the pendulum is speeding up.
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• Challenge (University Physics students should attempt answer Challenge questions; Principles of Physics and General College Physics may do so but it is optional for these students): It is obvious that a pendulum swinging back and forth speeds up at times, and slows down at times. How could you determine, by measuring positions and clock times, at what location a swinging pendulum starts slowing down?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
Again, determine the position of the pendulum according to a series of different clock times, with the interval between the clock times remaining constant. Each time the difference in the position of the pendulum is greater than the difference during the previous interval, the pendulum is speeding up at the beginning time of the interval. Once the difference in the position of the pendulum is less than the difference during the previous interval, the pendulum is slowing down.
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• Challenge (University Physics students should attempt answer Challenge questions; Principles of Physics and General College Physics may do so but it is optional for these students): How could you use your observations to determine whether the rate at which the tape is speeding up is constant, increasing or decreasing?
answer/question/discussion: ->->->->->->->->->->->-> (start in the next line):
If the difference in the position of the tape during each interval compared to the previous interval increases a constant amount, then the tape is speeding up at a constant rate. If the differences increase with each interval, then the tape is speeding up at an increasing rate. If the differences decrease with each interval, then the tape is speeding up at a decreasing rate.
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About 30 minutes.
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&#Very good work. Let me know if you have questions. &#