initial timing experiment

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.

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Initial Timing Experiment


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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).

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.

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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In this experiment, I used a full can of tomato paste, and the hardcover book: “The Visual Dictionary of Human Anatomy.” The ISBN is: 0-7894-0445-1. The higher end was propped up by a small paperback book. The can rolled smoothly and in a straight line. The can sped up as it rolled down the book.

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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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I used the millimeter rulers supplied in the lab kit to perform measurements. I collected measurements to the nearest millimeter and believe I was very accurate, within 1 mm. I performed each measurement three times and averaged the three numbers to collect the most accurate data. The higher end, propped up by a small paperback book, is 22mm higher than the low end. The diameter of the can is 121mm. The cover of the book is 411mm, so distance the can travels is 290mm. I used the TIMER program to do a total of four runs. The times were: 1.9375sec, 1.84375sec, 1.859451sec, and 1.725sec. Rotating the book 180 degrees I ran four more trials and received virtually identical times: 1.73742sec, 1.96388sec, 1.937sec, and 1.8265sec.

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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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To find the average speed of each run, I divided mm traveled by seconds to find this data run1: .00668mm/sec, run2: .00636mm/sec, run3: .00641mm/sec, run4: .00595mm/sec, run5: .00599mm/sec, run6: .00677mm/sec, run7: .00668mm/sec, run8: .00630mm/sec. Total average speed: .00639mm/sec. It’s very difficult to collect accurate data because the experiment happens so quickly. It appears that the average speed is accurate to the .001 because it doesn’t fluctuate from .006 very much.

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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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Trying to collect evidence to support the idea that the can is speeding up as it rolls down the incline, I split the incline into two even sections, (the 145mm mark) and performed three runs to clock the time it takes for the can to roll the first 145mm and then compare it to the total time I found in the previous exercises. For the first run, it took the can 1.109375sec to reach the 145mm mark. Two more runs found the can taking 1.140625sec and 1.20625sec to reach the mark. If you compare these times to the ones above, it takes more time to reach the halfway mark than it takes the can to go from the halfway mark to the end of the book. Thus, it speeds up.

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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: 

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It took 45 minutes to complete this experiment.

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You may add optional comments and/or questions in the box below.

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&#This looks very good. Let me know if you have any questions. &#