initial timing experiment

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.

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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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The book used for this experiment is titled Understandable Statistics. The ISBN number is 9780618949922. A full 4 oz. can of Kroger’s Green Chile Peppers was used as the rolling object. To prop the end of the textbook up, I used a white photo album which is approximately 2.8 cm thick. The object sped up, rolling smoothly in a straight line.

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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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The timing of the data was recorded using the timer program. The button was clicked when the can was released and again when the can reached the end of the book cover. The amount of time the can took to roll from one end to the other was found by subtracting to two times from one another. This was done three times for both directions.

The can traveled 28.3 cm (about 283 mm). This measurement was taken using a ruler about 30 cm long.

The propped end of the book was about 3.3 cm higher than the other end.

The times calculated the first three times were as follows: 1.964844 sec, 2.292969 sec, and 2.011719. The average of these three recorded times is 2.089844 sec. When the set-up was rotated 180 degrees, the measurements were as follows: 1.714844 sec, 1.78125 sec, and 1.8125 sec. The average of these measurements is 1.769531 sec.

I believe the times are accurate to the nearest one-hundredth of a second. The measurements in centimeters are to the nearest tenth of a cm.

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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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The average speed I calculated for the first calculation was 13.60 cm/sec. The average speed found for the reversed measurements was 16.00 cm/sec. These were calculated by dividing the distance traveled (28.3 cm) by each time recorded. After that, the three average speeds were added together and divided by 3. These seem to be as accurate as possible for each data set. However, I do not have any logical reasoning for why the reversed measurement speeds were so much faster than the others. The only reason I could come up with is that the table top surface I used was not as level as it appeared.

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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 confirm that the can was actually speeding up I taped five small pieces of paper on the side of the book with exactly 5 cm between each. Using the timer program, I clicked the time button as soon as the can was released and again each time the can passed a marker. Because the time in between each click decreased, I knew that the can increased in speed. The times listed in order are 0.496 sec, 0.375 sec, 0.25 sec, 0.21875 sec, and 0.109375 sec. This data supports that the can actually did speed up because the times are decreasing as the can moves further down the book.

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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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This experiment took me about 1.5 hours.

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

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&#Your work looks good. Let me know if you have any questions. &#