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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, and the following are position and clock times
0, 40.140
14, 40.906
17, 41.05
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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 determine the positions I would be within about two inches of the actual position. The video is blurry, so I had to guess where abouts the center of the roll was on the video when I paused it, and the roll looked about two inches in diameter.
The accuracy of the clock times would be in thousands, or accurate to +-0.001, I feel confident because this is when i paused the video, and this the accuracy given by the clock.
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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):
Between the three frames, I would find out the slope in a graph and see if one was larger than the other. So my first two measurements i would find the slope (change in position)/(change in time), and compare it to the second and third frame slope, again using (change in position)/(change in time). if the second calculation had a greater slope, i would say it travelled further in a shorter amount of time, therefore 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):
I would do the same as i did for the tape, but probably with four to six frames, and compare the differences in the (change in position)/(change in time), between two frames, against the next two frames, against the next two frames, until the end.
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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):
By measuring positions and clock times, I would utitlize six frames, one to start with the pendulum at rest, a second when it is a 1/4 thru one cycle, a third at approximatly half, a forth at 3/4, and the final when it comes to rest at the end of the cycle. At each of these times I would record the position and times of each frame, plot them on a graph, and compute the slope between each measurement.
The greater the slope, the faster the pendulum is swinging. and any peak or inflecton point could signify a change in acceleration or decelleration.
I do know that the pendulum speeds up until it hits the botom of the swing, then slows down as it rises to the end of its cycle.
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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):
Again I would take about 6 frames and record the position and times. From that data i would estimate the speeds by determining (change in distance)/ (change in time). So if the distance is greater over a shorter period of time, i would know that the tape roll is speeding up.
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&#Very good data and responses. Let me know if you have questions. &#