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PHY 201
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 pendulum in the first video (VID00425). The first measurement was at 59.359s and 3-1/4”. The second measurement was at 59.687s and 12”. The third measurement was at 59.906s and 16”.
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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):
It was very difficult to see any resolution of more than 1/2” because of the video quality and its encoding. The clock times, on the other hand, were very simple to read because they were displayed numerically, and accuracy could be expected of approximately 1000th of a second (three decimal places).
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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):
If the ratio of the change in position vs. the change in clock time is getting larger, the tape is accelerating. If the ratio of the change in position vs. the change in clock time is getting smaller, the tape is decelerating.
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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):
Similar to the tape rolling down the incline, if the ratio of the change in position vs. the change in clock time of the pendulum is getting larger, the tape is accelerating. If the ratio of the change in position vs. the change in clock time of the pendulum is getting smaller, the tape is decelerating.
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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):
Like stated above, you can tell if the pendulum is decelerating by measuring the position and clock times, and then comparing their ratios. If the position vs clock time ratio is getting smaller, then the pendulum is decelerating. The point at which that ratio is getting smaller is the point which the pendulum is decelerating.
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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):
The question above is asking how we can tell if the acceleration is increasing, staying the same, or decreasing, so we can compare the ratios of the change in acceleration vs the change in time from the data obtained in the last step. If those ratios are getting larger the acceleration is increasing, and if they're getting smaller, the acceleration is decreasing. If they are positive, they are accelerating, and if they are negative they are decelerating.
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&#Good responses. Let me know if you have questions. &#