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


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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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Objects used:

-Book Isbn #0-02-802833-3

-Used a marble for the rolling object

-I used a washer appx 2mm in width for the prop

-The ball rolled smoothly as I put a lighter on the edge of the inside of the cover to provide a steady incline so it wouldn't stray away.

-The acceleration seemed to be pretty constant.

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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 distance rolled = 26cm

The incline was roughly = 2mm the width of the washer

All was measured with a ruler and timed with the timer program.

Time Trial Book Turned Around 180 degrees

1. 1.75s 2.18s

2. 1.77s 2.31s

3. 1.78s 2.25s

Acceleration = 26cm/1.766s= 14.717cm/s

The possible error introduced may have been due to the instability of the book itself and the level of my desk, because when the book was turned around the measurements changed drastically. While the two sets of information are different they are consistent which leads me to believe that the measurements are accurate.

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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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Acceleration = 26cm/1.766s= 14.717cm/s

Took the average time it took for the three time trials and then divided by the distance. This leads to an accurate answer.

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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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I placed a paper clip at 5 different intervals, 5,10,15,20,26 cm respectively. I rolled the ball and took the time for each cm mark with three different trials and averaged them together. I made a graph of position vs time. The response is slightly parabolic, with the acceleration increasing with time.

Trial #1 Trial #2 Trial #3 Average

5cm .6875s .65625s .6785s .674s

10cm 1.09s 1.12s 1.08s 1.097s

15cm 1.335s 1.31s 1.35s 1.331s

20cm 1.5s 1.48s 1.42s 1.466s

26cm 1.81s 1.76s 1.73s 1.76s

Then just graph the info. Notice that the average is exactly what was determined in the previous problem. The marble is speeding up at an increasing rate and would continue to do so until it reached terminal velocity.

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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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45 min

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

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Excellent work.