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PHY 121
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):
In the first video, I chose to watch the tape roll at three different positions. The first position was at 59.140 seconds, when the tape is released at the top of the ramp. At 59.687 the tape reaches the middle of the measuring tape. The tape roll then hits the wall at 60.125.
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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):
To be honest, I couldn’t make a good predication at all because I can’t read what the measuring tape says. But if I could, I would say that based on the distance the camera is from the measuring tape, I could predict down to about two or three inches. This being based on the distance and then the actual size of the roll of tape as it covers up a few different marks. So I would say that based on this video I could have answers accurate to one or two inches and about .01 seconds with pausing times.
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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):
I would have to see the rate of acceleration of the tape (if any). I would start at a certain time (say 59) and see how long it takes the tape to get roughly 2 inches down the measuring tape (so from 0-2inchs) I would then compare that time to the 2-4 inches and if it were less time I know the tape is accelerating.
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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):
I would use the same ideology and apply it to the swing speed of the pendulum. How long does it take the pendulum to reach its peak on the left, and then again back to the right? Compare the two times and you can see roughly the acceleration of the pendulum.
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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):
As this is a challenge and I don’t need to do it, I am just going to approach the situation. I would say you would just have to take really precise time measurements, like pause the video every .1 seconds or something so you could measure the positions then. Then you would see that it speeds up as it reaches the bottom of the swing and then slows down at the top. Just a guess though.
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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):
Graph it! First reaction of course. I feel like a graph of position vs time would give you a pretty good curve, and you could then see when the graph is increasing at an increasing rate, increasing at a decreasing rate, etc. Calculus and derivitaves!
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Very good.
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&#Very good responses. Let me know if you have questions. &#