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course Phy 122
1/24 10 pm
Question: Suppose you measure the length of a pencil. You use both a triply-reduced ruler and the original ruler itself, and you make your measurements accurate to the smallest mark on each. You then multiply the reading on the triply-reduced ruler by the appropriate scale factor.
· Which result is likely to be closer to the actual length of the pencil?
Your answer:
I would me more apt to trust the original ruler. The triply-reduced ruler might give you a more detailed answer, but I believe that there are more discrepensies in the triply-reduced ruler than the original ruler.
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· What factors do you have to consider in order to answer this question and how do they weigh into your final answer?
Your answer:
You have to consider the amount of possible discrepencies and inaccuracies of both of the rulers. After consider these factors, I believe that although it may not be as accurate, the original sized ruler would have less errors.
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Question: Answer the same questions as before, except assume that the triply-reduced ruler has no optical distortion, and that you also know the scale factor accurate to 4 significant figures.
· Which result is likely to be closer to the actual length of the pencil?
Your answer:
Now, given that there is no optical distortions and the accuracy of the conversion factor, I believe that the triply-reduced ruler would be more accurate.
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· What factors do you have to consider in order to answer this question and how do they weigh into your final answer?
Your answer:
The security of the triply-reduced ruler having no optical distortions makes me believe that it is more accurate.
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Question: Suppose you are to measure the length of a rubber band whose original length is around 10 cm, measuring once while the rubber band supports the weight of a small apple and again when it supports the weight of two small apples. You are asked to report as accurately as possible the difference in the two lengths, which is somewhere between 1 cm and 2 cm. You have available the singly-reduced copy and the triply-reduced copy, and your data from the optical distortion experiment.
· Which ruler will be likely to give you the more accurate difference in the lengths?
Your answer:
I believe that the singly-reduced would give you the more accurate answer.
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· Explain what factors you considered and how they influence your final answer.
Your answer:
I believe that the singly reduced has less optical distortions than the triply reduced.
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Question: Later in the course you will observe how the depth of water in a uniform cylinder changes as a function of time, when water flows from a hole near the bottom of the cylinder. Suppose these measurements are made by taping a triply-reduced ruler to the side of a transparent cylinder, and observing the depth of the water at regular 3-second intervals.
The resulting data would consist of a table of water depth vs. clock times, with clock times 0, 3, 6, 9, 12, ... seconds. As depth decreases the water flows from the hole more and more slowly, so the depth changes less and less quickly with respect to clock time.
Experimental uncertainties would occur due to the optical distortion of the copied rulers, due to the spacing between marks on the rulers, due to limitations on your ability to read the ruler (your eyes are only so good), due to timing errors, and due to other possible factors.
Suppose that depth changes vary from 5 cm to 2 cm over the first six 3-second intervals.
Assume also that the timing was very precise, so that there were no significant uncertainties due to timing.
· Based on what you have learned in experiments done through Assignment 1, without doing extensive mathematical analysis, estimate how much uncertainty would be expected in the observed depths, and briefly explain the basis for your estimates. Speculate also on how much uncertainty would result in first-difference calculations done with the depth vs. clock time data, and how much in second-difference calculations.
Your answer:
I believe that the uncertainty will be quite low. Maybe somewhere from 10 - 30 percent. For both the first-difference calculations and the second-difference calculations.
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· How would these uncertainties affect a graph of first difference vs. midpoint clock time, and how would they affect a graph of second difference vs. midpoint clock time?
Your answer:
It would make the graphs open to larger possibility fields.
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· How reliably do you think the first-difference graph would predict the actual behavior of the first difference?
Your answer:
I think it would be fairly reliable.
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· Answer the same for the second-difference graph.
Your answer:
I also believe that this would also be very reliable.
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· What do you think the first difference tells you about the system? What about the second difference?
Your answer:
I believe it shows you the possibilities or range of the actual answer.
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Question: Suppose the actual second-difference behavior of the depth vs. clock time is in fact linear. How nearly do you think you could estimate the slope of that graph from data taken as indicated above (e.g., within 1% of the correct slope, within 10%, within 30%, or would no slope be apparent in the second-difference graph)?
Your answer:
I believe it could be done with much accuracy, although not perfect accuracy. I believe it would be within 30%, just to be safe.
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Again no extensive analysis is expected, but give a brief synopsis of how you considered various effects in arriving at your estimate.
Your answer:
I considered the possiblities and ranges of the accuracy of the measurements. I figured it had to be fairly accurate, but of course there had to be some discrepencies, so that is how I came to my conclusions, they may not be correct, but this was my best guess.
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&#This looks good. Let me know if you have any questions. &#