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Phy 201
Your 'initial timing 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.
** Initial Timing Experiment_labelMessages **
sorry for submitting this twice, I accidentally hit submit the first time without completely filling out the form
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Note: The majority of student report taking less than an hour on this experiment, though a few report significantly longer times.
Take reasonable care to get good data in this experiment. Try to do the timing as accurately as possible. Measurements of length, height, etc. should be reasonably accurate (e.g., with a meter stick or ruler you can measure to withing +- 1 millimeter, but it's not necessary to try to determine fractions of a millimeter).
In this experiment you will use the TIMER program, a hardcover book, the toy car that came in your lab materials package (or, if you do not yet have the package, a cylinder or some other object that will roll along the book in a relatively straight line), and a ruler or the equivalent (if you don't have one, note the Rulers link, which is also given on the Assignments page).
The book's cover should be straight and unbent.
The toy car (or other object) should roll fairly smoothly.
Place the book on a flat level tabletop. You will prop one end of the book up a little bit, so that when it is released the object will roll without your assistance, gradually speeding up, from the propped-up end to the lower end. However don't prop the end up too much. It should take at least two seconds for the ball to roll down the length of the book when it is released from rest. For a typical book, a stack of two or three quarters placed under one end works well.
Using the TIMER program determine how long it takes the ball to roll from one end of the ramp to the other, when released from rest. Once you've got the book set up, it takes only a few seconds to do a timing, so it won't take you long to time the object's motion at least three times.
Determine how far the object travels as it rolls from its initial position (where you first click the timer) to its final position (where you click at the end of the interval). This will probably be a bit less than the length of the book, due to the length of the object itself.
Determine how much higher one end of the book was than the other, and how far it is from the supports (e.g., the stack of quarters, or whatever you used to support one end) to the end of the book which rests on the table.
Then reverse the direction of the book on the tabletop, rotating the book an its supports (e.g., the stack of quarters) 180 degrees so that the ball will roll in exactly the opposite direction. Repeat your measurements.
In the box below describe your setup, being as specific as possible about the book used (title, ISBN) and the object being used (e.g., a can of vegetables (full or empty; should be specified) or a jar (again full or empty); anything round and smooth that will upon release roll fairly slowly down the incline), and what you used to prop the object up (be as specific as possible). Also describe how well the object rolled--did it roll smoothly, did it speed up and slow down, did it roll in a straight line or did its direction change somewhat?
your brief discussion/description/explanation:
I used the hard back book the Host ISBN: 978-0-316-06804-8
I used the regular sized marble that came in the initial materials packet, I also used 4 dimes stacked to prop the book up with. The object rolled smoothly and in a straight line, the object appeared to speed up as it went down the incline.
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In the space indicated below report your data. State exactly what was measured, how it was measured, how accurately you believe it was measured and of course what the measurements were. Try to organize your report so the reader can easily scan your data and identify any patterns or trends.
your brief discussion/description/explanation:
The length of the book was 24cm
The stacked end had a height of 5.5 cm
The unstacked end was 5.0 cm
The length from the stacked end to where the book meets the table was 24.5 cm
The first position of the marble rolling down the incline:
1) 355.8906
357.613
( a difference of 1.7224s)
2) 396.7344
398.5703
(a difference of 1.8359s)
3) 414.793
416.3867
(a difference of 1.5937s)
The second position of the ball rolling down the incline (rotated 180 degrees):
1) 511.2227
512.9336
(a difference of 1.7109s)
2) 526.7813
528.5117
(a difference of 1.7304s)
3) 544.8086
546.7891
(a difference of 1.9805s)
I think my measurements are as accurate as I am capable of. I carefully placed the ball so that it was in the same position every time, and stopped the timer when the ball reached the same position on the other end of the book. I do know that there are precision errors in the TIMER program and in myself.
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Using your data determine how fast the object was moving, on the average, as it rolled down the incline. Estimate how accurately you believe you were able to determine the object's average speed, and give the best reasons you can for your estimate of the accuracy.
your brief discussion/description/explanation:
the average of all six time measurements is: 1.6828s
the length traveled was 24 cm
24cm/1.6828s = 14.26cm/s
I think the accuracy is relatively high. There was of course human error when measuring and when clicking the mouse, and there was error in the precision of the TIMER program, but I was very careful when preforming the experiments, so given the circumstances I think my results are relatively accurate.
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How fast was the object moving at the beginning of the timed interval?
According to your previous calculation, what was its average speed during this interval?
Do you think the object, when it reached the lower end of the book, was moving at a speed greater or less than the average speed you calculated?
your brief discussion/description/explanation:
when the time interval began the object was at rest.
It would be 0cm/s
I think the object was moving at a speed greater than the average speed calculate when it reached the lower end of the book. Because the object sped up during the length of the book.
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List the following in order, from least to greatest. Indicate 'ties': The object's initial speed, its final speed, its average speed, and the change in its speed as it rolled from one end of the book to the other.
your brief discussion/description/explanation:
the objects initial speed was least, change in speed, average speed, final speed.
The object sped up, but the change in speed was not greater than its average speed during the entire length
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Devise and conduct an experiment to determine whether or not the object is speeding up as it rolls down the incline. If you have set the experiment up as indicated, it should seem pretty obvious that the object is in fact speeding up. But figure out a way to use actual measurements to support your belief.
Explain how you designed and conducted your experiment, give your data and explain how your data support your conclusions.
your brief discussion/description/explanation:
I used the same materials as before and marked a 12cm mark (half way) I hit the timer when I released the ball, when it hit half way, and when it hit the end of the book. I performed this three times:
1) 80.76172
81.73828
82.17969
2) 145.4063
146.3828
146.8242
3) 172.5234
173.3359
173.7734
The average time between the first two time intervals was: .9218s
The speed therefore was: 12cm/.9218s= 13.02cm/s
The average time between the second two time intervals was: .4401s
The speed therefore was 12cm/.4401s= 27.27cm/s
The rate of speed was actually doubled during the last half traveled compared to the first half traveled.
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The term 'rate of speed' doesn't make good sense, since speed itself is a rate. You would just say that the speed doubled, not that the rate of speed doubled.
This distinction is conceptually important.
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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?
1 hour
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You may also include optional comments and/or questions.
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*#&!
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Very well done.
Do check my notes.
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