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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Initial Timing Experiment
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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, 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 on the Assignments page).
• The book's cover should be straight and unbent.
• The 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.
• 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. Time the object's motion at least three times.
• Determine how far the object actually travels as it rolls from one end to the other.
• Determine how much higher one end of the book was than the other, and how far it is from one end to the other.
Then reverse the direction of the book on the tabletop, rotating the book and its prop 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?
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your brief discussion/description/explanation:
For this experiment I used our Physics textbook by Giancoli (ISBN# 9780130606204), and a full can of Hunts Tomato Paste (6oz, with a diameter of 5.4 cm). To prop up the end of the book, I used a small stack of index cards, measuring about 6 mm in height. The can of tomato paste rolled very smoothly, and speed up as it rolled down the book in a straight line.
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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 this experiment I measured the time it took for a full 6 oz can of tomato paste to roll down the cover of our Physics textbook, a length of 28.3 cm. I timed the can of soup rolling from one end of the book cover to the other 4 times and got the times: 1.805sec., 2.82sec., 1.946sec., and 2.133sec. At that point I turned the book with the notecards 180 degrees and measuring the rolling can again 4 times: 1.4375sec., 1.39844sec., 1.4375sec., and 1.36718sec.
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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:
Facing in the original direction, on average between the 4 trials the can was moving at a speed of 13.4 cm per second. When the book was rotated the can on average was moving at a speed of 20.1 cm per second. Given the range of time lengths on the first set of trials, the accuracy of the average speed, is probably not very well depicted. Contributing factors that can be attributed to human interaction could have manipulated the times (ie: pushing the can, or timing errors). The range of time lengths for the second set of trials is more consistent. In this case I would say the average speed calculated is fairly accurate.
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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:
To determine whether or not the object is speeding up, I set up basically the same experiment as before, but I also measured the half-way mark on the book and included a timing of when the can hit than mark.
Time from Start to Half-Way Point Half-Way point to End
Trial 1 .618125 seconds .523438 seconds
Trial 2 1.05468 seconds .55469 seconds
Trial 3 1.05469 seconds .60937 seconds
Trial 4 .66407 seconds .5625 seconds
The data is consistent with the can speeding up as it moves down the book cover, because in each trial the second half of the time is much shorter than the first half.
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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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&#Your work looks very good. Let me know if you have any questions. &#