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: I chose the tape roll. The position/times were: 4 inches at 20.343, 17 inches at 20.890, and 22 inches at 21.
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: I believe that I could make the observations from this video, with positions within 1 inch and within .001 seconds. Since the distance from the camera to the object is significant, it would be hard to pinpoint the measurement any closer than 1 inch. I chose 1 inch because visually I could see the black tick marks and that is how I would determine the distance. The computer with the time display makes it easier to pinpoint the time measurement down to .001.
• 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: If you took multiple readings of the tape rolling along, you could do an analysis (like the timer test) to see whether the time speeds up in increments. For example, you could calculate the time difference between 1 inch and 11 inches, and then from 11 inches to 21 inches. If the time increases with the second reading, then it could prove that the time is indeed increasing.
• 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: I would use the same observations and measurements as with the tape roll to try and determine whether the pendulum is speeding up or down. I would also use the position of the tape to determine whether it is moving faster than the pendulum to give me an idea of the speed as well.
• 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:
• 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:
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30 minutes
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&#Your work looks good. Let me know if you have any questions. &#