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.
** template formInitial Timing Experiment
You may enter any message or comment you wish in the box below:
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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 five 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 solid glass marble, a small can of tomato paste (full or empty?), a ball-point pen), 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?
Note: Don't trust this form. Compose your answer in Notepad or a word processor, saving it every few minutes, then copy and paste it into the box. Power could surge, your computer could malfunction, in any of a number of ways the work you put into this form could be lost. Compose it elsewhere and keep a copy.
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For my setup, I used my Giancoli Sixth Edition Physics book (ISBN 0-13-060620-0). This book is about 28.5 cm in length and right at 3.75cm in height. I used a domino that was provided in my physics lab kit to prop one end of the book with. This domino measures 5 cm. long by 2.5 cm wide and 1.0 cm tall. My ball was a can of Bush’s Baked Beans (full-1lb.) and the dimensions of this can are 11.25cm tall with a diameter of 7.5 cm.
My object rolled very smoothly the first three trials, increasing speed as it rolled in a straight line down the ramp. However, when I rotated everything 180 degrees, the can of beans really didn’t roll as fast as it had done before (I still got consistent time intervals but significantly slower). In each case, the beans rolled smoothly in a straight line gaining speed on the way down the ramp.
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In the box 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 see any patterns that might occur.
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During these trial runs, I recorded how fast the can of beans rolled down the incline (book) from a resting position. This was a distance of about 28.5 cm. Using the TIMER program, I recorded a time when the can started to roll and another time when the can reached the end of the book. I believe these measurements to be quite precise, even though the times recorded in the second set (after rotating everything 180 degrees) were much slower than the times taken in the first runs.
First set (0 degrees) Second set (rotating 180 degrees)
1.769531 sec 2.929668 sec
1.78125 sec 3.03125 sec
1.785156 sec 2.99218 sec
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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.
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Using my data, I was able to come up with calculations that determined how fast (on average) the can was moving down the length of the book. These values are as follows:
First set (0 degrees) Second set (rotating 180 degrees)
16.10596 cm/sec 9.72806 cm/sec
16.0 cm/sec 9.40206 cm/sec
15.96499 cm/sec 9.524828 cm/sec
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Devise and concuct 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.
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To figure out whether or not this can of beans was in fact speeding up, I used the following method:
1st: I measured the length of the book which was 28.5 cm.
2nd: I measured off three different intervals from start through 21.375 cm. Each mark was 7.125 cm apart……(1st mark-start = 0; 2nd mark = 7.125 cm; 3rd mark = 14.25 cm; 4th mark = 21.375 cm)
3rd: I measured the times between each mark and calculated to find the speeds between each interval and these are my findings:
0-7.125 cm interval 7.125-14.375 interval 14.250-21.375 interval
7.896066 cm/sec 12.49315 cm/sec 19.82608 cm/sec
7.761710 cm/sec 15.07437 cm/sec 19.97336 cm/sec
8.070796 cm/sec 15.32772 cm/sec 20.04395 cm/sec
As you can see, from beginning through 21.375 cm, the beans did in fact gain speed.
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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?
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This took me about 45 minutes to complete.
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You may add optional comments and/or questions in the box below.
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I was just wondering why my times were different (slower) after rotating the book 180 degrees? This doesn't make sense to me. I obtained similar times on the first three runs at 0 degrees but when I rotated it, I observed quite slower runs(all of which are consistent times).
It's likely your tabletop or countertop was tilted a bit.
&#Very good work. Let me know if you have questions. &#