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course PHY 202
1/25/15 at 9:20PMThis is a re-submission as I think I once again forgot to enter my access code the first time. My apologies!
Most queries in this course will ask you questions about class notes, readings, text problems and experiments. Since the first two assignments have been lab-related, the first two queries are related to the those exercises. While the remaining queries in this course are in question-answer format, the first two will be in the form of open-ended questions. Interpret these questions and answer them as best you can.
Different first-semester courses address the issues of experimental precision, experimental error, reporting of results and analysis in different ways and at different levels. One purpose of these initial lab exercises is to familiarize your instructor with your work and you with the instructor 's expectations.
Comment on your experience with the three lab exercises you encountered in this assignment or in recent assignments.
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Question: This question, related to the use of the TIMER program in an experimental situation, is posed in terms of a familiar first-semester system.
Suppose you use a computer timer to time a steel ball 1 inch in diameter rolling down a straight wooden incline about 50 cm long. If the computer timer indicates that on five trials the times of an object down an incline are 2.42sec, 2.56 sec, 2.38 sec, 2.47 sec and 2.31 sec, then to what extent do you think the discrepancies could be explained by each of the following:
The lack of precision of the TIMER program.
To what extent to you think the discrepancies are explained by this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
A lack of precision in the TIMER program is certainly possible, considering that issues such as lag may delay the program and cause an inconsistency between trials. The use of approximation by the program to find time may also lack precision due to inconsistency.
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The uncertain precision of human triggering (uncertainty associated with an actual human finger on a computer mouse)
To what extent to you think the discrepancies are explained by this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
I think this is the greatest source of discrepancy, between human error in determining when the ball comes to a stop or comes off the ramp, lag in neuromuscular response time between perception of the ball stopping and the actual response of the students finger on the mouse. It is also possible that the student clicks the mouse too early in anticipation of the ball stopping.
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Actual differences in the time required for the object to travel the same distance.
To what extent to you think the discrepancies are explained by this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
I think this is the factor that is least likely to cause discrepancies in trial time. Although this is possible due to variations in the ramp surface (leading to friction), the forces that act upon the ball down the ramp are more likely to be consistent than the TIMER program and/or human error.
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Differences in positioning the object prior to release.
To what extent to you think the discrepancies are explained by this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
As a facet of human error, discrepancies in positioning the ball could certainly be responsible for discrepancies in trial times. Positioning the ball slightly further up or down the ramp could increase or decrease run time, respectively. Unless the starting position was marked on the ramp for reference for future trials, it is very possible that this is the cause of trial time discrepancies.
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Human uncertainty in observing exactly when the object reached the end of the incline.
To what extent to you think the discrepancies are explained by this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
I mentioned this as a source of human error in my response on human clicking error, as anticipation or delay in response may cause erroneously-short or -long trial times. It is highly possible and likely that this causes trial discrepancies.
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Question: How much uncertainty do you think each of the following would actually contribute to the uncertainty in timing a number of trials for the ball-down-an-incline lab?
The lack of precision of the TIMER program.
To what extent to you think this factor would contribute to the uncertainty?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
Compared to the other sources of error, I think this factor is not as likely to contribute to uncertainty, but it certainly is a potential source.
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The uncertain precision of human triggering (uncertainty associated with an actual human finger on a computer mouse)
To what extent to you think this factor would contribute to the uncertainty?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
In my opinion, this is one of the most likely sources for trial run discrepancies because it is one of the least likely to be consistent.
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Actual differences in the time required for the object to travel the same distance.
To what extent to you think this factor would contribute to the uncertainty?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
This is the least likely of all factors to be a factor in uncertainty; variations in actual run time are probably negligible, particularly in comparison to human or program error.
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Differences in positioning the object prior to release.
To what extent to you think this factor would contribute to the uncertainty?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
Unless the start position is carefully marked so as to not deviate between trials, this factor is one of the most likely to cause uncertainty in trial time, behind click-time and human observation uncertainty.
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Human uncertainty in observing exactly when the object reached the end of the incline.
To what extent to you think this factor would contribute to the uncertainty?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
Along with click-time response, this is perhaps one of the greatest sources of uncertainty.
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Question: What, if anything, could you do about the uncertainty due to each of the following? Address each specifically.
The lack of precision of the TIMER program.
What do you think you could do about the uncertainty due to this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
The student can lessen the chance of computer lag time by closing unnecessary programs running in the background, but nothing can be done about program uncertainty without updates/fixes from the original programmer.
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The uncertain precision of human triggering (uncertainty associated with an actual human finger on a computer mouse)
What do you think you could do about the uncertainty due to this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
Practicing click-response could help in minimizing response time, as neuromuscular pathways that are frequently exercised are likely to get faster (to a certain degree) as the brain learns and practices the response pathway.
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Actual differences in the time required for the object to travel the same distance.
What do you think you could do about the uncertainty due to this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
Ensure uniformity in the ball and the ramp, if possible, particularly in the frictional differences that may arise in variations in the wood grain of the ramp.
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Differences in positioning the object prior to release.
What do you think you could do about the uncertainty due to this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
Mark the initial start position on the ramp and release the ball from that exact location at each trial.
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Human uncertainty in observing exactly when the object reached the end of the incline.
What do you think you could do about the uncertainty due to this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
The student should practice and also pick a consistent point at which the ball is considered to be off the ramp, then stop the timer when the ball reaches that exact point at each trial. This minimizes uncertainty in when exactly the ball is off the ramp. Avoid anticipation.
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&#Good responses. Let me know if you have questions. &#