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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 **
I submitted this on 6/7 at approximately 6:00
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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:
My setup included a smooth piece of wood that was 309 mm long, 19 mm thick, and 90 mm wide. I used this piece of wood because all the hardcover books I tried were not completely flat. The object that I used was a plastic water pipe (cpvc) that has an inside diameter of 16 mm and an outside diameter of 21, it was 30 mm long. I used 5 pennies that created a height of 7 mm that I placed completely covered at the edge of the wood. The object rolled relatively smooth and straight. This set up took place on my dining room table.
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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 set the pipe on the elevated end and using the timer released it and started the timer, I then the timer upon the pipe reaching the end of the board.
1st Trial from right to left: number seconds distance 1 2.05 309 mm 2 2.18 309 mm 3 2.27 309 mm
2nd Trial from left to right: number seconds distance 1 2.45 309 mm 2 2.52 309 mm 3 2.37 309 mm
The length of the board is extremely accurate; however my timing is less accurate due to me watching and timing at the same time.
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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:
For the trial as a whole I found that on average the pipe was going 133.8 mm/s. For the first trial, right to left, I found that on average the pipe was going 142.4 mm/s. For the second trial, left to right, I found that on average the pipe was going 126.1 mm/s. Using my given data, I believe that the average speed is accurate; however I have reservations concerning my timing.
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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:
-I do not have a way to determine how fast the pipe was moving at the beginning, but I believe it was moving at its slowest at the beginning.
-The average speed during this interval was 133.8 mm/s.
-I believe that the pipe was moving at a greater than average speed as it reached the end of the board.
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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:
From least to greatest: 1. The pipe’s initial speed 2. The pipe’s average speed 3. The pipe’s change in speed and the pipe’s final speed.
I came to this conclusion because the pipe’s initial speed is 0. The pipe’s average is a middle ground of the pipe’s times. The pipe’s change in speed and final speed are tied because the highest speed also equals the change in 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 the exact experiment right to left. I marked the board at its halfway point, 154.5 mm.
I then timed 3 trials: number time distance 1 1.51 154.5 mm 2 1.67 154.5 mm 3 1.43 154.5 mm
Taking the given data I found that the average speed was 100.3 mm/s. This speed is slower than the 133.8 mm/s average speed over the whole board.
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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 20 minutes
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Very well done.
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