course Phy 201
9/23/09 at 1230pm.again just wanted to remind you that im submitting all of the work i did for this class in the spring semester.
introductory pendulum experiment
Phy 201
Your 'introductory pendulum experiment' 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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Introductory Pendulum Experiment
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As on the first object-down-a-ramp experiment, this experiment doesn't require a major time committment. If you mess something up you get feedback and will be able to fix it. However, as before, do your best to get it right the first time.
In this experiment you will make a simple pendulum and observe how its frequency of oscillation varies with its length.
To make a pendulum tie a light string or thread around a relatively small dense object. In the absence of anything more convenient you could use a couple of CDs or DVDs with a string or thread tied through the middle. A smaller and denser object would be preferable, but not so much that you should take a lot of time trying to locate one. The string or thread should be about 4 feet long.
Hold the string so that the length from the point at which you are holding it to the center of the object is about equal to the distance from your wrist to your fingertips.
• Measure the length of this pendulum, from the point where you hold it to the center of the suspended mass, as accurately as you can.
• Start the pendulum oscillating, but don't make it swing too far--keep the distance from one end of the swing to the other less than half the length of the pendulum.
• Using a clock with a second hand, determine how many times this pendulum oscillates in 60 seconds. Repeat your count at least a few times, and continue until you are sure you know to the nearest whole cycle how many times it oscillates back and forth in a minute.
Repeat with a pendulum whose length is equal to the distance from your fingertip to your elbow.
Repeat once more with a pendulum whose length is equal to the distance from your toes to your hip.
In the box below
• Describe how you constructed your pendulum and out of what (what you used for the mass, its approximate dimensions, what it is made of, what sort of string or thread you used--be as specific as possible).
• Describe its motion, including an estimate (you don't have to measure this, just give a ballpark estimate) of how far it swung from side to side and how this distance varied over the time you counted.
• Give the lengths and the numbers of cycles counted, preferably in the form of a simple table so a reader can scan the data easily. Be sure you specify the units in which you measure the lengths (e.g., nanometers, millimeters, centimeters, inches, feet, miles).
• Describe what you mean by a 'cycle'. Different people might mean different things, but there are only a couple of reasonable meanings so as long as you describe what you mean we will all understand what you measured.
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@email.vccs.edu, 8, 103, .58
1@email.vccs.edu, 12, 84, .71
@email.vccs.edu, 16, 71, .85
@email.vccs.edu, 24, 60, 1
@email.vccs.edu, 32, 62, 1.15
@email.vccs.edu, 48, 42, 1.43
@email.vccs.edu, 64, 38, 1.58
@email.vccs.edu, 96, 30, 2
@email.vccs.edu, 128, 26, 2.31
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On a piece of paper sketch a graph of the number of cycles vs. the length of the pendulum.
• The lengths will go along the horizontal axis, the one usually labeled as the 'x axis'.
• The numbers of cycles will be represented on the vertical axis, the one usually labeled as the 'y axis'.
• Any time you graph quantity A vs. quantity B, you follow the 'y vs. x' convention with quantity A on the y or vertical axis, quantity B on the x or horizontal axis.
• Decide on a scale to use for each axis are mark off a consistent scale for each. The scale of one axis is independent of the scale of the other.
• Use a scale and graph size that will allow you to tell easily whether the three points on your graph lie on or close to a straight line, or whether the three points seem to lie on a nonlinear curve (i.e., a curve which is clearly not a straight line).
Imagine that you obtained an extensive data set, with hundreds of different lengths. Based on what you observed for your three lengths, and on your graph:
• What do you think the graph would look like?
• Would it be a straight line or a curve?
• Would it be increasing or decreasing? ... at an increasing or decreasing rate?
• What would happen to frequency as length became very small? What if length became very large?
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1. According to your graphs, complete the following tables
length in cm
number of cycles
time for one cycle
10, 90, .67
30, 54, 1.11
50, 40, 1.5
70, 35, 1.7
90, 32, 1.9
110, 28, 2.14
130, 25, 2.4
length in cm
number of cycles
time for one cycle
135, 10, 6
96, 30, 2
30, 50, 1.2
15, 70, .857
10, 90, .67
length in cm
number of cycles
time for one cycle
4, 120, 0.5
20, 67, 0.9
44, 46, 1.3
75, 35, 1.7
115, 28, 2.1
135, 24, 2.5
I can see that your information is good.
Had it been copied directly from a text editor or word processor, it probably would have lined up better and been more readable when posted.
2. Is the graph of # of cycles vs. length in cm constant, increasing or decreasing? Is it doing so at an increasing, constant or decreasing rate?
On this and on all questions, insert your answer after the 'Answer:' prompt, and include a brief explanation of how you arrived at your answer.
Answer: It is decreasing. At an increasing rate. It is decreasing because the number of cycles column is going down and at an increasing rate
because the length column is getting bigger as you go down the column or the graph.
3. Is the graph of time required for one cycle vs. length in cm constant, increasing or decreasing? Is it doing so at an increasing, constant
or decreasing rate?
Answer:It is increasing. Increasing rate. The graph is increasing at an increasing rate because both columns are getting larger as you go down
the graph.
4. How much difference is there between your first two lengths, and how much difference between the number of cycles counted in 60 seconds?
Answer:between the first two lengths there is 4 cm difference. And between the number of cycles there is 19
5. How much difference is there between your first two lengths, and how much difference between the corresponding times required to complete a
cycle?
Answer:There is 4 cm difference between the first two lengths. And there is only .13 seconds between the corresponding times.
6. How much difference is there between your last two lengths, and how much difference between the number of cycles counted in 60 seconds?
Answer: There is 32 cm difference between my last two lengths.And there is 4 cycles differencel in the 60 seconds.
7. How much difference is there between your last two lengths, and how much difference between the corresponding times required to complete a
cycle?
Answer:There is 32 cm difference between the last two lengths. and there was .31 seconds difference.
8. Is your graph of number of cycles counted vs. length in cm steeper, on the average, between the first two lengths or between the last two lengths?
Answer:Between the last two lengths because there is more of a difference in the numbers.
9. Is your graph of time required to complete a cycle vs. length in cm steeper, on the average, between the first two lengths or between the last
two lengths?
Answer:Between the last two lengths because there is more of a difference between those numbers.
10. The curve you sketched for your graph of (time required to complete a cycle) vs. (length) cannot possibly pass through the center of each of
your points. What is the greatest vertical distance between a point of your graph and the curve? What do you think is the least vertical distance?
(For example, in the figure below a curve has been constructed based on three data points. The first and third data point lie slightly above the curve,
the second point slightly below. The second point is probably the one which lies furthest from the curve, at a distance of approximately .03 vertical
units below. This distance is roughly estimated based on the scale of the graph. The first point is perhaps .01 vertical units above the curve, and
the third is perhaps .02 units above.)
Once you have inserted your answers, submit them by copying and pasting them into the box below:
The point at number 8. it is 32 cm between it and points 7 and 9. I think it is the second point because it is on 4 cm difference from points 1 and 3.
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Your instructor is trying to gauge the typical time spent by students on these experiments. Please answer the following question as accurately as you can, understanding that your answer will be used only for the stated purpose and has no bearing on your grades:
• Approximately how long did it take you to complete this experiment?
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I constructed my pendulum out of thread and a golden ring. size 5. It was normal sewing thread.
The pendulum swung steadly from side to side didnt go in a circle. I would say it was a little less than half the length of the thread I was using
at the time maybe 2 inches in most cases. As the ring slowed down it was not swinging as far. Maybe 1/2 inch.
One complete turn. When the ring started at one end and ended up at the other end that was one cycle.Starts at one extreme and returns to that point.
In order to get the periods of the nine pendulums you just divided the 60 seconds in a minute with the number of cycles that you got.The shorter
the string the less time it takes to reach your extremes.
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You may add optional comments and/or questions in the box below.
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It took me about 3.5 hours to complete this experiment
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Good work.
I have one disagreement with your answers to the questions. One of your graphs is indeed increasing and the other is decreasing, but neither is doing so at an increasing rate.
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