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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I used Giancoli’s Physics, ISBN 0-13-060620-0, for the book. I used a Bic Ultra Round Stic Grip pen for my cylinder. I used my cell phone (LG Envy), opened, to prop the book up. The pen rolled smoothly and seemed to speed up as it reached the bottom of the book. It veered slightly to the left as it descended.

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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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Trial 1- 2.5 seconds

Trial 2- 2.7 seconds

Trial 3- 2.4 seconds

Total Distance Traveled- 44.4 cm

Elevated end of book is 1.9 cm higher than the other.

After switching ends:

Trial 1- 2.2 seconds

Trial 2- 2.7 seconds

Trial 3- 2.5 seconds

Total Distance Traveled- 44.4 cm

Elevated end of book is 1.9 cm higher than the other.

The times were measured using the TIMER program. The length of the book and the elevation were measured using the metric rulers supplied in the lab kit. I believe the measurements are fairly accurate when considering inevitable human error.

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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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(2.5 + 2.7 + 2.4 + 2.2+ 2.7 + 2.5) / 6 = 2.5 seconds

44.4 cm / 2.5 seconds = 27.8 cm/second

I believe my calculation for the object’s average speed is quite accurate because the TIMER program provided accurate data. Any inadequacy came from human error through measuring the length and/or height of book.

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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 order to show that the object sped up as it rolled down the incline, I took measurements when the pen was halfway down the incline and at the end of the incline. My results show that it took the pen longer to reach the middle of the book than it did the end, so it took less time for the pen to travel the last half of the book. This shows that the pen’s speed increased as it went down the incline.

Trial 1- Halfway: 1.5 seconds

To end: .89 seconds

Trial 2- Halfway: 1.1 seconds

To end: .85 seconds

Trial 3- Halfway: 1.5 seconds

To end: .86 seconds

My data supports my conclusion that the pen’s speed increased as it traveled down the incline because it shows that it took longer for the pen to travel the first 22.2 cm than it did for the pen to travel the last 22.2 cm.

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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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30 minutes

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

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