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Phy 121
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 **
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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 put the book, Mountain Magic, on a hardwood floor and rolled a matchbox car down it. It was 11 inches long. I used my iPhone that measured about 1 cm wide as a support. The book, Mountain Magic, was slick on top, and it was fairly wide and long. It’s ISBN number 0-8499-5841-5. The car rolled very smoothly and in a straight line without changing direction but was gaining speed.
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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:
I measured the length of the book which was 11 inches long. I then measured the initial and final position of the car. I found that the initial position was 26037.3 and the final position was 26038.46. The support, my iPhone, measured about 1 cm so that was the difference in the slope from where the car started than where it ended. I then turned the book around 180◦ and did the same measurements. Again, the support, which was my iPhone, measured 1 cm and the car’s time at its original position was 26748.87 and at its final position was 26751.29.
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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:
11 inches/ 12 inches = .916/inch
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I don't think I see anything about 12 inches in your data.
If you divide 11 inches by 12 inches the inches divide out and you get .916, with no units.
However if you divide 11 inches by 12 inches / foot, which might have been your intention, you get .916 foot.
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.916/2 = .458 inches fast as it rolled down the incline
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You don't get speed by taking half the distance. The time required to travel the distance is part of the calculation.
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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:
The object was moving .3 seconds per inches at the beginning of the interval. Its average speed was about .916/inch. By the time it reached the lower end of the book it was moving at a greater speed than I calculated because it was it had been building up speed as it was doing down the incline.
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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:
Initial speed, change in speed, average speed, final speed
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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 set up my experiment the same way as before, but with a support that had more height to it than the one before. This time I used my calculator, which measured 2 cm instead of 1 but I used the same book, Mountain Magic that measured 11 inched long. I started my timer at the top when I released the car. The time that I released the car was 29463.4 and the time that I stopped it at when it reached its final position was 29464.17. So, to prove that it had sped up by the time it reached the bottom, I simply took the initial time and subtracted it from the final time to get 0.77. This proves that the car sped up by 0.77 seconds on its trek down the book.
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The time interval was .77 second.
However you need to use distance and time interval to figure out how fast it was moving.
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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?
45 minutes
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You may also include optional comments and/or questions.
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Your data are very good. However you need to modify some of your results, which haven't always been calculated correctly.
&#Please see my notes and submit a copy of this document with revisions, comments and/or questions, and mark your insertions with &&&& (please mark each insertion at the beginning and at the end).
Be sure to include the entire document, including my notes. &#
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