course PHY201 Š§ù’w°î¡¬²×¡Î©–ŽÈl‰Í‚ºÊassignment #000 000. `Query 0 Physics I 01-15-2008
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21:51:51 The Query program normally asks you questions about assigned problems and class notes, in question-answer-self-critique format. Since Assignments 0 and 1 consist mostly of lab-related activities, most of the questions on these queries will be related to your labs and will be in open-ended in form, without given solutions, and will not require self-critique. The purpose of this Query is to gauge your understanding of some basic ideas about motion and timing, and some procedures to be used throughout the course in analyzing our observations. Answer these questions to the best of your ability. If you encounter difficulties, the instructor's response to this first Query will be designed to help you clarify anything you don't understand. {}{}Respond by stating the purpose of this first Query, as you currently understand it.
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RESPONSE --> To ensure our applicability to this class and our ability to comprehend the basics necessary for continuance.
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21:52:20 If, as in the object-down-an-incline experiment, you know the distance an object rolls down an incline and the time required, explain how you will use this information to find the object 's average speed on the incline.
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RESPONSE --> distance traveled/time = vAve confidence assessment: 3
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21:53:26 If an object travels 40 centimeters down an incline in 5 seconds then what is its average velocity on the incline? Explain how your answer is connected to your experience.
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RESPONSE --> 40cm/5sec= 8 cm/sec These quantities are very close to measurements we students might have taken in our experiment. confidence assessment: 3
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21:55:15 If the same object requires 3 second to reach the halfway point, what is its average velocity on the first half of the incline and what is its average velocity on the second half?
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RESPONSE --> 20cm/3sec=6.667 cm/sec on the first half 20cm/2sec=10cm/sec on the second half. confidence assessment: 3
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21:59:26 Using the same type of setup you used for the first object-down-an-incline lab, if the computer timer indicates that on five trials the times of an object down an incline are 2.42 sec, 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 thefollowing: {}{}a. The lack of precision of the TIMER program{}{}b. The uncertain precision of human triggering (uncertainty associated with an actual human finger on a computer mouse){}{}c. Actual differences in the time required for the object to travel the same distance.{}{}d. Differences in positioningthe object prior to release.{}{}e. Human uncertainty in observing exactly when the object reached the end of the incline.
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RESPONSE --> a. very little - the timer program is much more accurate than the number of sig figs shown b. very high. Human response is approx 0.2 seconds which is a large error within the amount of time being measured. c. small compared to the accuracy we are aiming for - surely gravitational, atmospheric and frictional differences are dismissable in this case d. medium due to lack of human ability to place the cylinder in the same location and release in the exact manner each trial e. very high as discussed in b. above confidence assessment: 3
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22:02:32 How much uncertainty do you think each of the following would actually contribute to the uncertainty in timing a number of trials for the object-down-an-incline lab? {}{}a. The lack of precision of the TIMER program{}{}b. The uncertain precision of human triggering (uncertainty associated bLine$(lineCount) =with an actual human finger on a computer mouse){}{}c. Actual differences in the time required for the object to travel the same distance.{}{}d. Differences in positioning the object prior to release.{}{}e. Human uncertainty in observing exactly when the object reached the end of the incline.
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RESPONSE --> a. none over an average of a large data set b. possibly none if the human error averages out to zero but a fair likelyhood exists of predisposition to trigger habitually early or late c. zero d. none over an average of a large data set e. same as discussed in b. above confidence assessment: 3
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22:05:30 What, if anything, could you do about the uncertainty due to each of the following? Address each specifically. {}{}a. The lack of precision of the TIMER program{}{}b. The uncertain precision of human triggering (uncertainty associated with an actual human finger on a computer mouse){}{}c. Actualdifferences in the time required for the object to travel the same distance.{}{}d. Differences in positioning the object prior to release.{}{}e. Human uncertainty in observing exactly when the object reached the end of the incline.
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RESPONSE --> a. use a timer triggering device interfaced directly to the computer calibrated to allow for delay in the electronics and the device's mechanics b. same as a. above c. perform in a vacuum, confirm lack of seismic, geomagnetic and gravitational fluctuations d. fabricate a mechanical gate to position and release the cylinder e. same as a. above confidence assessment: 3
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22:07:22 According to the results of your introductory pendulum experiment, do you think doubling the length of the pendulum will result in half the frequency (frequency can be thought of as the number of cycles per minute), more than half or less than half?
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RESPONSE --> The ratio is variable throughout the range (realted to slope of a curve) and therefore the answer depends on the data itself confidence assessment: 3
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22:08:32 Note that for a graph of y vs. x, a point on the x axis has y coordinate zero and a point on the y axis has x coordinate zero. In your own words explain why this is so.
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RESPONSE --> Because if the value were anything other than zero the point would not lie on the axis confidence assessment: 3
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22:10:28 On a graph of frequency vs. pendulum length (where frequency is on the vertical axis and length on the horizontal), what would it mean for the graph to intersect the vertical axis (i.e., what would it mean, in terms of the pendulum and its behavior, if the line or curve representing frequency vs. length goes through the vertical axis)? What would this tell you about the length and frequency of the pendulum?
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RESPONSE --> In such a case the pendulum would have a negative length and a positive frequency. I am not sure how a negative length pendulum could be constructed. Perhaps it is question of quantum construction confidence assessment: 2
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22:11:14 On a graph of frequency vs. pendulum length, what would it mean for the graph to intersect the horizontal axis (i.e., what would it mean, in terms of the pendulum and its behavior, if the line or curve representing frequency vs. length goes through the horizontal axis)? What would this tell you about the length and frequency of the pendulum?
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RESPONSE --> The pendulum would have a positive length but a negative frequency. I do not think this to be possible. confidence assessment: 2
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22:12:20 If a ball rolls down between two points with an average velocity of 6 cm / sec, and if it takes 5 sec between the points, then how far apart are the points?
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RESPONSE --> v=d/t d=vt=6cm/s*5s=30cm confidence assessment: 3
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22:12:42 On the average the ball moves 6 centimeters every second, so in 5 seconds it will move 30 cm. {}{}The formal calculation goes like this: {}{}We know that vAve = `ds / `dt, where vAve is ave velocity, `ds is displacement and `dt is the time interval. {}It follows by algebraic rearrangement that `ds = vAve * `dt.{}We are told that vAve = 6 cm / sec and `dt = 5 sec. It therefore follows that{}{}`ds = 6 cm / sec * 5 sec = 30 (cm / sec) * sec = 30 cm.{}{}The details of the algebraic rearrangement are asfollows:{}{}vAve = `ds / `dt. We multiply both sides of the equation by `dt:{}vAve * `dt = `ds / `dt * `dt. We simplify to obtain{}vAve * `dt = `ds, which we then write as{}`ds = vAve *`dt.{}{}Be sure to address anything you do not fully understand in your self-critique.
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RESPONSE --> ok self critique assessment: 2
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22:17:59 You were asked to read the text and some of the problems at the end of the section. Tell me about something in the text you understood up to a point but didn't understand fully. Explain what you did understand, and ask the best question you can about what you didn't understand.
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RESPONSE --> Percentage uncertainty and percent error were two somewhat new terms to me. I am used to dealing with tolerances which are defined. These two ideas seem to indicate making assumptions. Presumable from the text of the order of one unit whose decimal place is the last decimal place in the data. It would seem logical to me that the strict use of measuring standards and sig figs would better define these units. confidence assessment: 2
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22:19:45 Tell me about something in the problems you understand up to a point but don't fully understand. Explain what you did understand, and ask the best question you can about what you didn't understand.
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RESPONSE --> Again the uncertainty calculations are new to me. I think I get the general idea but I am not confident in making assumptions of how much uncertainty to divide. confidence assessment: 2
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