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 a number of observations of positions and clock times. The point here is to think about how you would use that information if you did go to the trouble of collecting it.
If you did take observations of positions and clock times, how accurately do you think you could determine the positions, and how accurately do you think you would know the clock times?
answer/question/discussion:
If the positions and clock times were observed, then the clock time would be accurate within +/- .001 sec and the position would be accurate within +/- 1/8 inch.
The clock time is displayed to three decimal places so its accuracy should be to three decimal places. The position in relation to the measuring tape is only accurate to within one unit of the smallest unit of measurement.
How can you use observations to determine whether the tape rolling along an incline is speeding up or slowing down?
answer/question/discussion:
You could measure the speed at which the tape traveled from point a to point b then from point b to point c, then from point c to point d, etc. Then review those speeds to determine if the tape is speeding up or slowing down. If the speed is increasing between each point, then the tape is speeding up. If it is decreasing then it is slowing down.
you can measure positions and clock times, with some uncertainty, but you can't directly measure speed from the information on the video
How can you use your observations to determine whether the swinging pendulum is speeding up or slowing down?
answer/question/discussion:
In the same manner as for the tape, by measuring the speed at several different points. If the speed is increasing between each point, then the pendulum is speeding up. If it is decreasing then it is slowing down.
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:
By measuring the speed at which the pendulum travels between two points for several areas on the path of travel. Then plot a graph of speed vs. distance. The graph will show the point at which the pendulum begins to slow down.
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:
Plot the speed vs. time on a graph. If the slope of the line on the graph is steeper when traveling up to the right, then the speed is increasing. If the slope is not changing then the speed is constant. If the slope is decreasing steeply toward the bottom right, then the speed is decreasing.
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45 minutes
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You have a very good understanding of these ideas, but your answers are based on the idea that you can measure speed from these videos. You can measure positions and clock times, which you can then use to infer information about speed, but speed is an instaneous quantity that must be inferred.
How would you use the position and clock time information to answer these questions?