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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Initial Timer Experiment

The setup used for this experiment consisted of my sixth edition Physics book by Douglas Giancoli, ISBN 0-13-060620-0. The book’s dimensions are: length of 28.3 cm, width of 22.1 cm and a height of 3.7 cm. The cylindrical object used was a new tube of Chap-et stick lip balm. A gem CD case with a height of 0.5 cm, width of 14.2 cm and 12.4 cm in length was used to prop up one end of the Physics book. The experiment took place on my computer desk.

The Chapstick rolled smoothly down the book. There was some hesitation of the Chapstick at the top of the book but it picked up speed fast all the way to the end of the book where it rolled off. The Chapstick rolled consistently 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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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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he first part of the experiment was done with the top of the book and the prop on my right side and the bottom of the book on my left side. The top of the book was propped up 0.5 cm with the object traveling approximately 28 cm. The times obtained were taken from the start of the object rolling from the top of the book until it rolled to the end of the book.

First Run

2.546875

2.359375

2.125

2.296875

2.03125

The second part of the experiment was done the same except I put the top of the book and the prop on my left side and the bottom of the book on the right. These times were also obtained from the start of the object rolling from the top of the book until it rolled to the end of the book.

Second Run

2.53125

2.453125

2.453125

2.1875

2.234375

The timer program was used to time the experiment. The times are fair in accuracy, the accuracy is only as good as reaction time of the experimenter.

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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 the average speed I took how far the object traveled, approximately 28 cm and divide it by the times given. I then added the speeds in both runs and divided it by 10.

First Run

28 / 2.546875 = 11 cm / sec

28 / 2.359375 = 11.9 cm / sec

28 / 2.125 = 13.2 cm / sec

28 / 2.296875 = 12.2 cm / sec

28 / 2.03125 = 13.8 cm / sec

Second Run

28 / 2.53125 = 11.1 cm / sec

28 / 2.453125 = 11.4 cm / sec

28 / 2.453125 = 11.4 cm / sec

28 / 2.1875 = 12.8 cm / sec

28 / 2.234375 = 12.5 cm / sec

The average speed of all the samples taken is 12 cm / sec. I estimate the accuracy to be + / - 0.1 cm / sec. I estimate this accuracy to be + / - 0.1 cm / sec because I rounded the speeds to the nearest 0.1 cm / sec.

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

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conducted my own experiment using everything in the original experiment. In this experiment I divided my book in half, at 14 cm. I marked the lower half with masking tape. I then timed the roll of the Chapstick at the start, the middle and the end. I did two runs of 5 observations each.

First Run

First Half Second Half

1.359375 .734375

1.21875 .78125

1.21875 .734375

1.03125 .828125

.984375 .78125

Second Run

First Half Second Half

1.15625 .8125

1.296875 .65625

.921875 .828125

1.0625 .765625

.90625 .78125

In all observations it can be noted that the second half of the roll that the Chapstick gained speed because in all observations it takes longer from the start of the object rolling to the middle of the book than from the middle of the book to the end of the book.

1 hour and 30 minutes

Very good report, and good data.