initial timing experiment

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

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).

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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I propped the Physics textbook (0130606200) lengthwise on a single cd jewel case. I used an empty 12 oz size coke can to roll. It rolled smooth and in nearly a straight line each time down the incline.

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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 can rolled 11 inches on top of the book.

The book was raised 1/4 inch on one side.

I believe my measurements were fairly accurate because I used a ruler to hold the can in place at the top of the incline at the same spot for each time it was rolled.

Time (seconds)

Roll #1 2.296875

Roll #2 2.40625

Roll #3 2.296875

Roll #4 2.265625

Roll #5 2.265625

After 180 degree rotation

Roll #1 2.34375

Roll #2 2.484375

Roll #3 2.3125

Roll #4 2.40625

Roll #5 2.359375

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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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Out of the 10 rolls, it took an average of 2.3436875 seconds to move down the incline. The can moved at an average rate of .2130625 inches/second. I think I accurately found the can's average speed because I divided the average time it took to move down the incline by the distance it traveled.

Good explanation, but note that the division would go the other way--divide inches by seconds to get inches/second. It appears that you divided the opposite way.

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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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In this experiment I rolled the can halfway down the incline and stopped it , then I noted the time. Then I rolled the can down the second half of the incline and noted the time.

Roll # Top half (seconds) Bottom half (seconds)

1 1.703125 1.65625

2 1.609375 1.46875

3 1.5 1.53125

4 1.421875 1.5

5 1.546875 1.59375

I added the amount of time it took for the can to travel both halves of the incline for 5 rolls, which was 15.53125 seconds. By dividing 15.53125 by the amount of times rolled (5 rolls), I got an average time of 3.10625 seconds for each roll. Because this average time is higher than the average time found in the last average, which was 2.3436875 seconds, it suggests that the can does speed up if it is not stopped halfway down the incline.

That supports your conclusion very nicely. Very good.

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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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about 30 minutes

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

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You did good work on this experiment, and reported it very nicely. Be sure to see my notes.