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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.
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• Follow the instructions, fill in your data and the results of your analysis in the given format.
• Regularly save your document to your computer as you work.
• When you have completed your work:
Copy the document into a text editor (e.g., Notepad; but NOT into a word processor or html editor, e.g., NOT into Word or FrontPage).
Highlight the contents of the text editor, and copy and paste those contents into the indicated box at the end of this form.
Click the Submit button and save your form confirmation.
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 titled: Chemistry. The ISBN is 0-13-199323-2. The object I used to roll down the book was the toy that I received in my lab kit. To prop the book up I used a pencil that layed on its side. The toy car rolled very smoothly. It started off slower and began to speed up and rolled in a pretty straight direction.
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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:
In my report I measured the length that the car rolled, which was 27.5 cm from start to finish. I also measured the table to the top of the book on the incline side which was 5 cm, as well as the table to the top of the book on the lower end which was about 4.25 cm. The distance from the pencil, which I propped the book up with, to the end of the ramp was about 24 cm. I measured these distances with the ruler document you supplied in our lab kit. After measuring this data, I timed how long it took for the car to roll down the ramp at three different positions, the middle (at 13.75 cm), the bottom middle (at 20.625 cm) and the bottom (at 27.5 cm). I did this twice, once after rotating the book 180 degrees. I timed this using the timer that I downloaded. Here are the results:
Book on a slant (seconds) Book rotated 180
Middle .6875 .6563
Mid Bottom 1 1.0157
Bottom 1.2969 1.2345
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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:
In the first trial I estimated that the car was moving approx. 20.61 cm/sec. (In trial 2 it was about 21.18cm/sec) I believe I was fairly accurate on this average. Aside from the lag between my eyes/brain/hand movements I am confident my answer is pretty accurate. The reason I think it is accurate is because I found the avg. speed for each different spot on the slope that I timed and then I averaged those together. This will take into account that the car was slower at the beginning and faster at the end.
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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 obj. was moved 13.75 cm in .6875 seconds at an average of 20 cm/sec at the beginning of my time interval for Trial 1. In trial 2 it moved 13.75cm in .6563 seconds at an average of 20.95cm/sec at the beginning of the time interval. I believe that the car was moving faster at the lower end of the book than it was in the higher end.
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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:
For Trial one: Change in speed (.93 cm/sec),Initial Speed (20cm/sec), Avg speed (20.61 cm/sec), Final Speed (21.20 cm/sec)
For Trial two: Change in speed (1.08cm/sec), Initial Speed (20.95cm/sec), Avg. Speed (21.18cm/sec), Final Speed (22.28cm/sec)
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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:
In order to determine that the car was speeding up as it rolled down the incline. I did the same type of experiment but used a long board instead of a book and made it so the ramp was longer. This way I would have more times to measure the speed of the car. The ramp was about 80 cm long (ply wood). I chose to use the timer again and get a clock time for the middle of the first half (20 cm), the half (40 cm), the middle of the bottom half (60 cm) and the bottom (80 cm). The results were as follows.
Time Avg speed cm/sec.
Middle of 1st Half 1.609 12.43
Middle 2.062 19.4
Middle of bottom half 2.421 24.78
Bottom 2.685 29.8
Total avg speed is 21.6. The data supports my conclusion because there is a larger difference between the times at the beginning of the wood board to the end. This is easier to see than the book because it was a longer slope and the car rolled for a longer period of time. It was also more spaced out while doing the time trials and easier to time.
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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?
This took me approx. 1 hour and a half.
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You may also include optional comments and/or questions.
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Please copy your document into the box below and submit.
&#Your work on this lab exercise looks very good. Let me know if you have any questions. &#