course Phy 121 assignment #001001.
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12:53:25 `questionNumber 10000 Explain in your own words how the standard deviation of a set of numbers is calculuated.
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RESPONSE --> The standard deviation is the square root of the average of all the squared deviations. The deviations are how far from teh mean the samples are. confidence assessment: 3
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12:54:30 `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 --> Fittina a straight line for a graph is used when there are multiple points on a graph and you are trying to get the best fit line. Usually, th line will not run through any of the points, but wiill try to lie as close to the poitns as possible. Two people may have two differnt vertical intercepts depending on how they drew their best fit lines. confidence assessment: 3
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12:55:27 `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 distance / time. It is related to rate because a rate is a change in something over another change in something, in this case change in distance over change in time. confidence assessment: 3
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12:55:32 `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 --> ok self critique assessment: 3
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12:55:53 `questionNumber 10000 Given average speed and time interval how do you find distance moved?
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RESPONSE --> you would multiply time * speed to get distance moved. confidence assessment: 3
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12:55:59 `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 --> ok self critique assessment: 3
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12:56:23 `questionNumber 10000 Given average speed and distance moved how do you find the corresponding time interval?
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RESPONSE --> time = distance / average speed confidence assessment: 3
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12:56:29 `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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12:56:57 `questionNumber 10000 Given time interval and distance moved how do you get average speed?
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RESPONSE --> average speed = distance / time interval confidence assessment: 3
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12:57:21 `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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???????????z? assignment #001 ???g???w?y???? Physics I Vid Clips 06-05-2007
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15:27:19 `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 --> The velocity is increasing as it goes down the ramp.
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15:27:33 `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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15:28:30 `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 if the speedometer shows us greater and greater speeds as it rolls down the slope.
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15:28:52 `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
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15:29:47 `questionNumber 10000 What is the shape of the velocity vs. clock time graph for the motion of the ball?
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RESPONSE --> The shape of the graph is increasing at an increasing rate.
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15:30:37 `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 --> I didn't think the graph would be linear, but now it makes sense that it would be if it were at a constant incline.
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??s???????w??????assignment #001 ???g???w?y???? Physics I Class Notes 06-05-2007
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15:36:32 `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 --> The graph would look like an upsidedown u because the velocity would be faster at the beginning and then tail off at the end.
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15:36:49 `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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15:37:30 `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 --> The ball would be increasing at an increasing rate. It would look like a u on a graph.
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15:37:58 `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 -->
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