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

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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To complete this assignment, I used my Physics textbook “Sixth Edition Physics Giancoli”, a can of Value Time Condensed Chicken Noodle Soup (full), it was propped up using a ball point BIC pen. The can rolled smoothly in a straight line, and speed 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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The textbook was 28cm long, 21.5 cm wide. The propped up end of the textbook was 1cm high. The time was 1:74 seconds, 1:49 seconds, and 1:51 seconds. I believe that the measurements are accurate and it seemed that the can picked up speed as it rolled down the textbook.

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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 of the can rolling down the text book was 17.8 cm/s. By taking the average distance traveled and dividing it by the average time it took for the can to roll down the textbook, I came to the conclusion that the average speed was 17.8cm/s.

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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 find whether or not the can was speeding up, I looked for the average acceleration. My conclusion was that the average acceleration was 11.3 cm/s.

You weren't asked to find the average acceleration, so it's no problem, but this looks like about half the average acceleration; it looks like you divided your average velocity by the time interval, when acceleration is change in velocity divided by time interval. We'll see that soon. Note also that units of acceleration are cm/s^2, not cm/s.

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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 approximately 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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&#Your work looks good. See my notes. Let me know if you have any questions. &#