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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 rolling tape to view and three different positions.
Position 1: 59.468 at 4in
Position 2: 59.687 at 12 in
Position 3: 59.906 at 19.5 in
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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):
If I had a series of several positions vs clock time, I could use it to calculate the rate the tape is rolling down the incline. As far as accuracy, this time would be the most accurate. It can be seen on the clock to the nearest .001 of a second. The position’s accuracy could only be estimated to the nearest inch. It is very hard to pinpoint any closer measurement than that because of the blurring of the camera when paused. My results would therefore only be approximate results.
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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):
You can determine the rate when it first starts to the rate covering the total distance and the time it takes to cover that distance, and then compare to see if the tape rolling is 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: ->->->->->->->->->->->-> (start in the next line):
If you obtain enough data points and calculate the rate, rate = distance/time, between each point, you can determine if, and where, the pendulum is speeding up or slowing down. What makes this type of measurement an approximation is determining an exact time and an exact distance from the video tape. I can pause the video at two different distances and the time hasn’t changed. If you could take still pictures from a camera, the data might be more accurate.
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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):
The answer to this question is what was described above: collect several data points of distance and corresponding time. Measure the rate between each point. Notice where the object slows in rate or increases in rate and from that determine at what location the swinging pendulum starts slowing down. Again, accuracy is difficult to determine when measuring distance using a video camera because of the blurring of the picture when pausing. It’s almost impossible to measure more precise than to the nearest inch.
The answer to this question
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&#This looks good. Let me know if you have any questions. &#