course PHY 121 I got some very weird results due mainly to the timing error in the preceding experiments i think.
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02:22:42 `q001. Experiment 4. Acceleration is constant for an object rolling down a uniform incline. By timing an object as it accelerates from rest for various distances down an incline, we infer its average acceleration for various distances and average speeds. We then test to validate the hypothesis that the acceleration is in fact uniform lawn the incline. See the corresponding video files on CD #0 (see note in red at the top of this document) entitled Introductory Video Experiments, video clip #4. Describe what you see in the clips. How do you determine by timing the acceleration of an object accelerating at a uniform rate from rest?
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RESPONSE --> I have already answered most of these My computer froze up and had to be shut down.
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02:22:50 `q001. Experiment 4. Acceleration is constant for an object rolling down a uniform incline. By timing an object as it accelerates from rest for various distances down an incline, we infer its average acceleration for various distances and average speeds. We then test to validate the hypothesis that the acceleration is in fact uniform lawn the incline. See the corresponding video files on CD #0 (see note in red at the top of this document) entitled Introductory Video Experiments, video clip #4. Describe what you see in the clips. How do you determine by timing the acceleration of an object accelerating at a uniform rate from rest?
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RESPONSE --> ok
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02:22:54 You determine the acceleration using the fact that when initial velocity is zero and acceleration is uniform, the final velocity is then double the average velocity. Average velocity is defined to be the displacement divided by the time interval required for the displacement to occur.
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RESPONSE --> ok
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02:23:00 `q002. You may use some of your data from the preceding experiment. By timing a ball as it rolls from rest through distances of 10, 15, 20, 25, 30, 35, 40, 45 and 50 cm down a uniform incline, we determine whether the acceleration on the incline seems to be related to either the distance the ball rolls down the incline or to its average velocity on the incline. Which data from the preceding experiments is relevant to this experiment?
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RESPONSE --> ok
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02:23:02 In the experiment immediately preceding this one the ball on the first ramp traveled the given distances, presumably with uniform acceleration. You can therefore use your data from that experiment.
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RESPONSE --> ok
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02:23:04 `q003. Present your data in a clearly labeled and organized table. Determine the average acceleration corresponding to each distance, and present your analysis in a table showing each significant quantity calculated. Explain how each column of your table is calculated from previous columns.
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RESPONSE --> ok
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02:23:07 Your first table should have shown the distances `ds from 5 cm to 50 cm and the corresponding times `dt required to travel those distances. Your analysis should have shown for each distance your results for average velocity vAve = `ds / `dt, final velocity, change in velocity and rate of change of velocity. The should have included clear explanations of how each of these quantities was obtained from the preceding quantities.
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RESPONSE --> ok
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02:23:09 `q004. Graph a point corresponding to acceleration vs. distance for each timing. Be sure you know which quantity goes on which axis (review the instructions for the pendulum experiment if you do not know). Sketch the straight line you believe best fits your data points. Do not try to go through any point on your graph, but rather try to get as close as possible on the average to your data points. Then pick two points on this straight line. Give the coordinates of the points you have picked, including units. Then calculate the rise, run and slope between these points, again including units. Give your results.
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RESPONSE --> ok
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02:23:13 If you got good data, your straight line should have been fairly near horizontal. It should ideally be difficult to tell whether the line should rise or fall. This is because ideally the acceleration will be independent of the distance traveled. However, due to timing errors and other factors this might not be the case. How convinced are you that your data do not indicate a horizontal slope?
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RESPONSE --> ok
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02:23:21
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RESPONSE --> ok
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02:37:32 `q005. Analyze errors: Using a procedure similar to that of the preceding experiment, determine the uncertainty in the acceleration for each point (Principles of Physics: analyze only the 10-, 30- and 50-cm points) and indicate these uncertainties on your graph as explained under Q & A on the homepage, under topic Error Bars, Rectangles and Linearity. Is it possible to draw a straight horizontal line that passes between the error bars or within the error rectangle for every graph point? Explain why, if it is so, then we have good support for the hypothesis that the acceleration on the ramp is constant.
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RESPONSE --> I used +/- 1 cm for the distance error uncertainty and .2 for the acceleration., because I know there are some timing errors. It is still not possible to draw a horizontal line that passes between the error bars or within the error rectangle for every point. I could draw a line that would pass throogh the points for the 10 and 50 cm points. However even though my results do not determine that the hypothesis has good support, I believe that the data should show this.
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02:38:52 Unless you are an experienced timer, the uncertainty in timing is probably +-.05 sec or more. Even with this sort of uncertainty, it is not uncommon, due to systematic errors in timing and other factors, or the corresponding error regions to be such that it is not possible to draw a straight line through every region. However, in most cases it is indeed possible. In cases were it is not possible, usually there is only a point or two where the error regions make this impossible.
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RESPONSE --> Yes, I agree, If I had analyzed the other points ( 15, 20, 25, etc.) most would have fallen on a horizontal best fit line.
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02:38:59 005.
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RESPONSE --> ok
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