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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: ->->->->->->->->->->->-> scussion (start in the next line):
I choose to observe the tape roll in Video 2. 1. Clock Time - 40.678; 9 inches. 2. Clock Time 41.015; 17 inches 3. Clock Time 41.125; 20.5 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: ->->->->->->->->->->->-> scussion (start in the next line):
I don't think I could accurately predict the positions. The tape gets blurry as it accelerates. Its very difficult to do any better than a half inch, but even that doesn't leave me feeling very comfortable. The clock is much better because that is digitia, although I did catch at one point that the clock image was fuzzzy as if I was about to see a new time appear. So I would conclude that the distance could be measured to the nearest inch and the time could be measured to the nearest .1 My reasoning is that beyond these distances and times, the blurriness would make anything more accurate impossible.
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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: ->->->->->->->->->->->-> scussion (start in the next line):
You could plot these times and positions on a graph. If the graph was linear, it would mean the speed was constant. If the graph had a curve, you would know if it was speeding up or slowing down.
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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: ->->->->->->->->->->->-> scussion (start in the next line):
You could again plot the points on a graph. The curve, if there was one, would tell you if it was speeding up or 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): 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: ->->->->->->->->->->->-> scussion (start in the next line):
It was not obvious to me that the pendulum was speeding up at times and slowing down at others. I would have to take multiple views and really be able to go frame by frame an again I would use a graph to determine where the increase or decrease in speed occurred.
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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: ->->->->->->->->->->->-> scussion (start in the next line):
As with the penculum, I would try to get as many data points as possible and then graph the results to see where and to what degree the tape was speeding up.
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&#Very good responses. Let me know if you have questions. &#