phy 201
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:
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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.
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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: The pendulum is the first thing that catches you eye so I used it to take measurements and determined the position of the tape to it. The first time is when the pendulum and the tape are first released: 40.140. The second time is when the pendulum reached the end of the ramp the tape was on: 41.453. The third time was the time the pendulum went back to its starting position: 42.765.
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:
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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: This could be done accurate due to the timer and the measuring tool. My age is going to determine the speed at which I hit the stop button on the video quick enough to view the clock with clarity and accuracy. Several times I had to restart my observations because the timer would stop at a point all numbers were blurred. That could have been the number needed to be accurate. It is accurate within .4 seconds because the timer wouldn't give me a more accurate number within the 100ths or 1000ths with the blurred numbers. I got my estimate by taking the number I could read clearly and close the area I was trying to time and measure.
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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: Stop the timer in three spots, beginning, middle and end. Subtract the first time with the second time. Then subtract the second time with the third time. The time it took for the first half of the experiment was lower then the time it took to reach the end. Therefore the tape was 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: Same as the way I answered the tape question only the pendulum slowed 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:
*Gravity plays a large part in the speed of the pendulum. So it should speed up when it is returning to a perpendicular or vertical position and slow down swinging up and away from the force of gravity.
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: One would have to stop the timer, measure the distance it moved in at least 5 positions: center, midway to the left of the fulcrum and its furtherest distance in a swing and midway right of the fulcrum, them at its furtherest distance both right and left. By measuring those point in time, one could determine in what position is the pendulum its fastest.
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30 minutes
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Very good work on this exercise.