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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:
The way that I set up this experiment was that I used my Human Anatomy and Physiology Ninth Edition Book ISBN number 0-321-74326-1; I used a domino as the object that created the slope, and a small red marble as the object that was rolled. The marble rolled smoothly down the book, it increased in speed and rolled in a straight line. I think that the reason for the increase in speed was because of the slope of the book.
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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 time between the starting points that the marble was released 3 times both in a regular position and in a reversed position. The times that were in a regular position include:
Trial 1- 1.332031 seconds
Trial 2- 1.25 seconds
Trial 3- 1.316406 seconds
While the times in the reversed position include:
Trial 1- 1.34375 Seconds
Trial 2- 1.324219 Seconds
Trial 3- 1.308594 Seconds
I believe the accuracy of the data that was collected is as close as it could be to being accurate. The explanation with the data is that the seconds that it took to get from point A to point B is relatively constant. The distance between the two points remained the same, in both directions.
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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 three different speeds that I recorded for the three trials I did were:
Trial 1- 16.89149877
Trial 2- 18
Trial 3- 17.09199138
To get these speeds, what I did was take the length between the starting point and the ending point, which was 22.5 cm, and then I divided that by the seconds it took to go from the starting point to the ending. The average speed I think would be about 17 cm per second. The accuracy of my findings were based on I knew the time in seconds it rolled, and I found the length it rolled, then did some basic division.
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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 in the beginning was not moving very fast maybe 2 or 3 cm per second. On the average, I believe the marble was rolling down the incline at a rate of 17 cm/s. I believe that I was able to determine the accuracy pretty easy, because I divided the distance from point A to point B, which is 22.5 cm, by each of the times separately. Then added the results together and found the average to be 17 cm/s. When the object reached the lower end of the book, it was moving at a greater speed.
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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:
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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 designed my experiment the way the directions described; I placed the domino underneath the book in the center. Then I placed the marble at the top in the center and released the marble. When I released the marble I would click the button on the timer that stated “click to time event” and then when the marble would reach the bottom I would hit that button again. I think that my data supports that distance and time plays a factor in the speed it takes to reach a certain point.
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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.
I wasn’t too familiar with how to find the initial or the final speed; I would like to know how to do that. I left that question blank, but I can always go back in and edit it, if everything about this lab isn't correct. I really tried, but I just couldn't figure it out.
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The initial speed for each of these trials was zero; each object was or should have been released from rest.
You calculated average velocities. The average velocity will be between the initial and final velocities.
If the acceleration is uniform, then the average velocity will be exactly halfway between the initial and final velocities.
Having found the average velocity, then, the question becomes: What final velocity, averaged with the initial velocity of zero, will give you the average velocity?
You'll see much more about this as you work through the assignments.
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&#Good responses. See my notes and let me know if you have questions. &#