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Mth 158
Your 'question form' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
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Mth 158
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I haven't had the opportunity to complete the orientation part of the class due to a vacation with limited internet access. I do plan to finish it by the end of the week. Also, I don't have the book and CD's yet. Would it be possible to do that part of the work once I do have them.
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@& You should wait until you get the book and disks before doing the Orientation part about running the disks.*@
@& However do try to get these soon.*@
PHY 121
Your 'response to key systems intro _ phy 1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
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September 6, 2011 at 7:18 p.m.
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. View and respond to videos of some fundamental systems
The videos listed below can be downloaded directly and played with QuickTime (if you can play YouTube, you can play these). If you wish you can save them to be replayed later. File sizes range from 1.6 to 5 megabytes. Average length of clips is about 25 seconds.
These videos show a few fundamental systems that represent a lot of what we study in first-year physics. Many labs in your course will be based on similar systems, which can be set up using items in your Initial Materials package. You should view these videos and consider the questions posed within them, as well as the questions that accompany the links in this document.
Physics II students will of course be on familiar ground with many of these questions, which will for them constitute a reminder and refresher. Some of the later videos are of systems that will not be studied until second-semester physics, but which can at least be observed by Physics I students/ Everyone can speculate freely in their answers.
Unless otherwise indicated, all physics students should observe these clips and think about their answers to these questions.
You should view the video clips below, and think about the associated questions. You will then be asked to submit your answer using the form Responses to Questions about Key Systems. Be sure to see the form for instructions before composing your answers.
• Pendulum equilibrium, frequency, amplitude, period
The pendulum and its motion are almost universally studied in first-semester physics. For Physics I students this is a brief introduction to the pendulum. Physics II students will likely be familiar with the terminology and the behavior of the pendulum.
What do we mean by equilibrium, frequency, amplitude and period of a pendulum?
Equilibrium - position when pendulum is straight down
Frequency - number of times a pendulum completes a cycle in a given period of time
Amplitude - distance from equilibrium position to extreme position
Period of a Pendulum - time required to complete an over and back cycle
• Pendulum frequency and length
The pendulum and its motion are almost universally studied in first-semester physics. For Physics I students this is a brief introduction to the pendulum.
Do the period and frequency of a pendulum depend on its length? If so, how?
Yes. The longer the length the lesser the frequency and the greater the period. The shorter the length the greater the frequency and the lesser the period.
• Marble from rest down incline then to table
Objects accelerating down inclines are almost universally studied in first-semester physics, as are freely falling objects (e.g., the marble between the end of the incline and the table).
What measurable quantities change when we change the slope of the incline?
The position at which the marble first contacts the blue piece of foam (on which it ultimately lands) changes with the slope of the incline. If we continue increasing the slope of the incline, will this position keep changing, and how?
The slope, speed and distance the marble travels.
I would say it would, that the position the marble lands would begin increasing as the slope increased and at some point begin decreasing as the steepness of the slope increases.
• Straw rotating on die
Rotational motion is in many ways as simple as straight-line motion. Rotational systems often keep moving longer (objects moving in straight lines tend to run into things), and they keep passing the same position, so in some ways they are easier to observe.
Through how many degrees do you estimate the straw rotated, and how long did it take to come to rest after the push? So on the average, through how many degrees per second was it rotating?
How long did it take to complete its last 180-degree rotation? Through how many degrees per second was it moving, on the average, during the last 180 degrees?
Are there measurements you could take to confirm the obvious fact that the system is slowing down?
I estimate the straw rotated 360 degrees, took 6 seconds to come to a complete stop, and travels at about 60 degrees per second.
It took around 4 seconds to travel the last 180 degrees, traveling at 45 degrees per second.
You could look at the time it took to complete the first 180 degrees, 2 seconds and travels at 90 degrees per second. This shows it is slowing down.
• Pendulum, washer, simultaneous drop and release
Did the pendulum hit the wall before or after the dropped washer hit the table?
What could you change in order to make the two hit at the same instant? There are a number of answers to this question; try to think of as many as possible.
How close in time would the two events have to be before you would be unable to detect the difference?
The pendulum hit after the bolt.
You could increase the height of the drop of the bolt, shorten the length of the pendulum, or shorten the distance of the pendulum from the wall.
It would have to be close, like within 1/100th of a second.
• Chain of rubber bands in series, ends pulled further apart
This system exhibits many of the most important aspects of wave motion.
What observable quantities indicate increasing tension as the ends of the rubber band chain are gradually puller further and further apart?
Is there any indication that the rubber band on the right end of the chain is under greater or lesser tension than the rubber band on the left? Is there any indication that the rubber band in the middle is under greater or lesser tension than either of the ends? Given the rubber bands and paper clips, how could we investigate these questions?
You could measure the tension by the length the rubber bands stretched to.
Yes. The rubber band on the right appears longer than the others.
I would say that they are lesser due to the expansion of the open paper relieving tension.
We could measure the different lengths of the rubber bands between the paper clips at different increments of expansion.
• Flow from a uniform cylinder
This system, and similar systems, can be used to gain a great deal of insight into the behavior of fluids.
Does the water level in the cylinder decrease at a constant, an increasing or a decreasing rate as time goes on?
Does the horizontal distance traveled by the falling water stream change at a constant, an increasing or a decreasing rate?
Does the amount of water exiting the cylinder per second increase or decrease as time goes on? Does it increase or decrease at an increasing or decreasing rate?
What could we measure to determine the speed of the water as it exits the cylinder?
Does the speed of the water exiting the cylinder increase, decrease or remain the same as it falls?
(Physics II students only): Does the gravitational potential energy of the system change with time? If so, how?
How are the answers to the above questions related?
I would say decreasing because of the visual change in the stream of fluid coming out of the cylinder.
The fluid exits at a decreasing rate.
The fluid decreases at a decreasing rate.
Measure the depth of the cylinder and document how much time it takes to reach certain measurements.
Remain the same??
They are all in relation to the amount of pressure put on them by the air causing the fluid to exit the cylinder.
• Domino Stack
Everyone should observe the system, but only Physics II students are expected to attempt answers to the questions.
Does the stack have greater potential energy before being stacked or after, or is the potential energy the same for both?
Does the stack have greater kinetic energy before being stacked or after, or is the kinetic energy the same for both?
If we know the mass of a domino and its height relative to the tabletop, how do we find its gravitational potential energy?
If we know the mass of a domino and its velocity, how to we find its kinetic energy?
If a domino is removed from the top of the stack and placed on the tabletop, does the potential energy of the system change? If the entire stack, except for the bottom domino, is moved off the bottom domino and placed on the tabletop, does the potential energy of the system change? Which final state of the system has the greater potential energy?
• Beads in shaking, inclined metal box
Everyone should attempt to answer these questions, but this system is particularly relevant to Physics II students. Physics II students should of course try to work their knowledge of Physics I into their answers, but this is a complicated system and at this point all answers will be considered good answers.
The box shakes back and forth from left to right. The box is inclined so that the end away from the camera is higher than the end closer to the camera. So how is it that some of the beads manage to 'climb' toward the 'high' end?
What do you think is the average ratio of the number of beads in the 'upper half' of the box to the number in the 'lower half'?
There are 4 large beads, 4 small beads and 7 medium-sized beads in the box (call this a 4-4-7 proportion). What percent of the beads in the box are of each size? Do you think the beads that make it to the 'upper half' are in the same proportion? How could you obtain data to measure this?
Because the beads are not only bouncing from side to side but also off of one another and off of the angles of the box.
2/3 in the lower portion, 1/3 in the upper
27%, 27%, 46%
I would think that the smaller would more often make it to the top. You could measure this by observation.
• Rubber band chain pulse, transition, fundamental
Everyone should attempt to answer these questions, but this system is particularly relevant to Physics II students. Physics II students should of course try to work their knowledge of Physics I into their answers, but this is a complicated system and at this point all answers will be considered good answers.
If you look at the video frame-by-frame you can probably see the pulse as it propagates down the chain. It becomes harder to see as it reflects back toward the far end, and becomes almost completely obscured before it starts its second trip toward the camera. It's worth trying to trace the pulse.
The pulsing motion is gradually replaced by a simple back-and-forth motion of the chain. Why do you think this occurs?
Because the energy exerted by the reaction evens out through the change and is dispersed evenly.
• Rubber band chain fundamental, length changed, frequency changes
Everyone should attempt to answer these questions, but this system is particularly relevant to Physics II students. Physics II students should of course try to work their knowledge of Physics I into their answers, but this is a complicated system and at this point all answers will be considered good answers.
The frequency of the back-and-forth motion of the chain decreases when the chain gets shorter and increases when the chain gets longer. Why do you think this happens?
Because the frequency increases with the tension on the rubber bands.
&#This looks good. Let me know if you have any questions. &#