course Phy201 ONjzճ̱assignment #001
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18:18:06 `questionNumber 10000 Physics video clip 01: A ball rolls down a straight inclined ramp. It is the velocity the ball constant? Is the velocity increasing? Is the velocity decreasing?
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RESPONSE --> I believe the velocity increases at a constant rate. The increase in velocity is constant because the incline is straight and constant. The velocity increases because of the affect of gravity pulling on the object .
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18:18:39 `questionNumber 10000 ** It appears obvious, from common experience and from direct observation, that the velocity of the ball increases. A graph of position vs. clock time would be increasing, indicating that the ball is moving forward. Since the velocity increases the position increases at an increasing rate, so the graph increases at an increasing rate. **
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RESPONSE --> ok
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18:20:18 `questionNumber 10000 If the ball had a speedometer we could tell. What could we measure to determine whether the velocity of the ball is increase or decreasing?
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RESPONSE --> We could measure the acceleration and the speed at which it is traveling.
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18:22:22 `questionNumber 10000 ** STUDENT RESPONSE: By measuring distance and time we could calculate velocity. INSTRUCTOR COMMENTS: The ball could be speeding up or slowing down--all you could get from the calculation you suggest is the average velocity. You could measure the time to travel the first half and the time to travel the second half of the ramp; if the latter is less then we would tend to confirm increasing velocity (though those are still average velocities and we wouldn't get certain proof that the velocity was always increasing). You would need at least two velocities to tell whether velocity is increasing or decreasing. So you would need two sets of distance and time measurements. **
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RESPONSE --> Ok to obtain a measurement we would need to measure the distance and time of travel in two separate locations on the incline to determine wheter the velocity is increasing or decreasing.
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18:23:48 `questionNumber 10000 What is the shape of the velocity vs. clock time graph for the motion of the ball?
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RESPONSE --> I believe that it would be a diagonal line that begins at the origin and travels upward to the top right of the graph.
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18:24:49 `questionNumber 10000 ** If the ramp has an increasing slope, the velocity would increase at an increasing rate and the graph would curve upward, increasing at an increasing rate. If the ramp has a decreasing slope, like a hill that gradually levels off, the graph would be increasing but at a decreasing rate. On a straight incline it turns out that the graph would be linear, increasing at a constant rate, though you aren't expected to know this at this point. All of these answers assume an absence of significant frictional forces such as air resistance. **
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RESPONSE --> ok
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18:26:13 `questionNumber 10000 A ball rolls down ramp which curves upward at the starting end and otherwise rests on a level table. What is the shape of the velocity vs. clock time graph for the motion of the ball?
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RESPONSE --> It would begin as a linear increase then curve to decrease as the ball slows on the level area.
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18:27:41 `questionNumber 10000 ** While on the curved end the ball will be speeding up, and the graph will therefore rise. By the time the ball gets to the level part the velocity will no longer be increasing and the graph will level off; because of friction the graph will actually decrease a bit, along a straight line. As long as the ball is on the ramp the graph will continue on this line until it reaches zero, indicating that the ball eventually stops. In the ideal frictionless situation on an infinite ramp the line just remains level forever. **
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RESPONSE --> ok,
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18:29:27 `questionNumber 10000 For the ball on the straight incline, we would certainly agree that the ball's velocity is increasing. Is the velocity increasing at a constant, an increasing, or a decreasing rate? What does the graph of velocity vs. clock time look like?
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RESPONSE --> It would increase at an increasing rate and would rise with each increase.
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18:30:32 `questionNumber 10000 ** It turns out that on a straight incline the velocity increases at a constant rate, so the graph is a straight line which increases from left to right. Note for future reference that a ball on a constant incline will tend to have a straight-line v vs. t graph; if the ball was on a curved ramp its velocity vs. clock time graph would not be straight, but would deviate from straightness depending on the nature of the curvature (e.g., slope decreasing at increasing rate implies v vs. t graph increasing at increasing rate).**
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RESPONSE --> I thought it would be linear then changed my mind. I should have went with my first instinct.
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{Lwxɓ֣֯z assignment #001 ONjzճ̱ Physics I Vid Clips 06-13-2008 [Ȍs̼ЪR°͉ assignment #000 000. `Query 0 Physics I 06-14-2008
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19:59:03 `questionNumber 0 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 --> The purpose of this query is to gauge my understanding of ideas about motion and timing through the labs.
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19:59:38 `questionNumber 0 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 --> You can divide the distance by the time to obtain the average speed. confidence assessment: 3
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20:01:10 `questionNumber 0 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 = 8cm/sec. This is the formula that I used to calculate the average speed in my initial timing experiment. confidence assessment: 3
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20:03:19 `questionNumber 0 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 = 6.7cm/sec for the first half of the incline. 8.0-6.7 = 1.3cm/sec for the second half of the incline. confidence assessment: 2
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20:09:10 `questionNumber 0 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. The Timer program is only precise to the nearest tenth of a second. b. There is some uncertainty in the precision of the human trigger. Probably within 0.5 sec. c. There is probably little difference in the time for the object to travel the same distance each time. I would estimate +/- 0.001sec. d. I would say the object is positioned within +/- 0.0001cm of the same position each time. e. I would say there is probably +/- 0.05sec of uncertainty for the human observing the object reaching the end of the incline. confidence assessment: 2
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20:11:26 `questionNumber 0 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. +/-.1sec B. +/- 0.05sec. c.+/- .001sec. d. +/- .001cm e. +/-.001sec confidence assessment: 2
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20:12:33 `questionNumber 0 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 --> I think that doubling the length will result in less than half the frequency. confidence assessment: 3
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20:14:43 `questionNumber 0 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 --> I am not sure if I understand why this would be unless each point would cross each axis through a linear line. confidence assessment: 0
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20:16:04 `questionNumber 0 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 --> The length became very small and the frequency increased greatly. confidence assessment: 2
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20:16:55 `questionNumber 0 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 length became larger and the frequency decreased greatly. confidence assessment: 2
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20:18:55 `questionNumber 0 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 --> average velocity * time = distance 6cm/s * 5sec = 30cm confidence assessment: 3
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20:19:13 `questionNumber 0 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: 0
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20:23:19 `questionNumber 0 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 --> As a Chemistry major with just one more semster after this one, I am very familiar with significant figures, the SI system, conversions, and dimensions. How do you calculate % uncertainty for a measurement. confidence assessment: 3
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20:26:33 `questionNumber 0 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 --> I understand all of the problems except #'s 5, 6, 10, 11 . Those require calculation of % uncertainty and approximate uncertainty. I do not understand how to calculate uncertainty. confidence assessment: 3
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݈ٳˡYw˙nڞ assignment #001 001. Physics I 07-01-2008
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12:15:11 `questionNumber 10000 Explain in your own words how the standard deviation of a set of numbers is calculuated.
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RESPONSE --> It is calculated by taking the square root of the average of the squared deviaitons. confidence assessment: 2
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12:20:11 `questionNumber 10000 Explain in your own words the process of fitting a straight line to a graph of y vs. x data, and briefly discuss the nature of the uncertainties encountered in the process. For example, you might address the question of how two different people, given the same graph, might obtain different results for the slope and the vertical intercept.
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RESPONSE --> The line can be estimated by eyeballing the line that best fits between all of the points without usually touching any of them with approximately the same distance between the points and the line. The answer can be different for different people because it's just an estimate. One person could determine the rise and run and slope using the two farthest points on the graph and then determine the y intercept by extending the line through the y axis. The other person could choose a point on the graph and solve the equation for the y intercept . confidence assessment: 1
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12:22:42 `questionNumber 10000 Briefly state what you think velocity is and how you think it is an example of a rate.
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RESPONSE --> Velocity is the change in speed with respect to time. It is a rate because speed is a rate of distance with respect to time. confidence assessment: 1
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12:24:26 `questionNumber 10000 ** A rate is a change in something divided by a change in something else. This question concerns velocity, which is the rate of change of position: change in position divided by change in clock time. **
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RESPONSE --> Velocity is the change in position divided by the change in clock time and is a rate because it is a change in something divided by a change in something else. self critique assessment: 3
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12:25:31 `questionNumber 10000 Given average speed and time interval how do you find distance moved?
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RESPONSE --> distance = speed divided by time confidence assessment: 3
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12:26:18 `questionNumber 10000 ** You multiply average speed * time interval to find distance moved. For example, 50 miles / hour * 3 hours = 150 miles. **
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RESPONSE --> I was thinking backwards. It would be multiplied instead of divided. self critique assessment: 1
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12:27:13 `questionNumber 10000 Given average speed and distance moved how do you find the corresponding time interval?
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RESPONSE --> distance divided by average speed would give the time interval. confidence assessment: 3
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12:27:27 `questionNumber 10000 ** time interval = distance / average speed. For example if we travel 100 miles at 50 mph it takes 2 hours--we divide the distance by the speed. In symbols, if `ds = vAve * `dt then `dt = `ds/vAve. Also note that (cm/s ) / s = cm/s^2, not sec, whereas cm / (cm/s) = cm * s / cm = s, as appropriate in a calculation of `dt. **
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RESPONSE --> ok self critique assessment: 3
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12:28:11 `questionNumber 10000 Given time interval and distance moved how do you get average speed?
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RESPONSE --> Divide the distance by the time interval to get average speed. confidence assessment: 3
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12:28:24 `questionNumber 10000 ** Average speed = distance / change in clock time. This is the definition of average speed. For example if we travel 300 miles in 5 hours we have been traveling at an average speed of 300 miles / 5 hours = 60 miles / hour. **
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RESPONSE --> ok self critique assessment: 3
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ȧۯ̌歍ӫ܇M assignment #001 001. Physics I 07-01-2008