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PHY 231
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 book I used was The Princeton Review Cracking the New GRE 2012, ISBN: 978-0-375-42819-7. I used a medium sized marble, and the object I used to prop the book up was a small square pin holder that is about 2.5 centimeters long and 1.5 centimeters tall. The marble rolled smoothly at an even pace, and it did change direction somewhat.
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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:
First I used the TIMER program to time how long it took for the object to roll down the book, I started the timer as soon as I let go of the marble, and stopped it as soon as it fell off of the book, I feel it was measured fairly accurately because they were all in .01 seconds of each other. The measurements were: .9492188, .9921875, and .9609376. Then I measured how long the object traveled from where the marble was when I released it to where it dropped off, I believe this measurement was accurate also. The measurement was: 25.8 centimeters. After that, I measured the difference between the height of the book at the propped side and the height of the book at the un-propped side. The propped side was 5.4 centimeters and the un-propped side was 3 centimeters, so the difference is 2.4. The last thing I did was measure the book length from the support to where it touches the table, to do this I laid the ruler flat on the table and measured from one length to the other, which was very accurate. The measurement was 27 centimeters. I did the exact same thing but rotated the book 180 degrees and got these times: .9648438, .9375, and .9882813. How long the object traveled was: 25.7 centimeters. The book height was 5.4 centimeters on the propped side and 3 centimeters on the un-propped side, making the difference: 2.4 centimeters. The book length from the support to where it touches the table was 27 centimeters.
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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 object was moving, on the average, as it rolled down the incline at 26.67 centimeters per second. I believe this is about 80 percent accurate, because I used all the times and got an average time, then I combined the two lengths of how far the object traveled and got an average for that. After that all I had to do was divide them so I could get a centimeter per second ratio.
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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 0 centimeters per second at the beginning of the timed interval. The average speed during this interval was 27.18 centimeters per second. I think the object was moving at a speed greater than the average speed I calculated because the speed is increasing at an increasing rate.
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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 object speeded up by .3417 centimeters per second from the start of the book to the end of the book. The objects initial speed was 24.6448 centimeters per second. The objects average speed was 26.67 centimeters per second. The objects final speed was 27.9865 centimeters per second.
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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 by using the all the same resources from this experiment. I then timed the marble at different parts of the book from the start to middle, and then from the middle to end. This way I could see if the time was shorter or longer when it reaches the last half of the book, and it was. The time it took for the marble to reach the middle was: .5234375 seconds, and the time it took for the marble to reach the end was: .460935 seconds.
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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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&#Good work. Let me know if you have questions. &#