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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I did not receive a bead or wire necessary for the initial pendulum experiment in my initial materials kit. There are two balls, but neither have holes for inserting the wire and there is no wire.

Those materials are in the Standard Lab Kit. They are not required for the Introductory Pendulum Experiment, which can be done with the thread and just about any object to which you can tie the thread; however the washer in the kit is a very good choice for that object.

The first time the bead is needed is in the 'Assignment 0' experiments, which are now in Assignment 5.

I'll pack your standard lab kit today and it will be available sometime late this afternoon. I'll email you to acknowledge; be sure to let me know if you don't get the message.

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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 my physics book with a length of 28 cm, ISBN 0-13-060620-0, propped up by a 1 cm thick post-it note pad. The object was a bic ball point pen. It rolled fairly smooth but is not balanced around it's center so I had to make sure I started it with the lettering on top which was the heavy side and allowed the roll to begin. Otherwise it would not start. It sped up as it moved 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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I did 5 tests under both conditions using the timer with the following results:

Test #1: 1.78125, 2.078125, 2.0625, 1.78125, 1.78125

Test #2: 1.59375, 1.828125, 1.875, 1.859375, 1.796875

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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 object traveled 28 cm in an average of about 1.9 seconds or an average speed of 14.7 cm/sec

Because the travel time of 2 seconds is so small, the error introduced by variations on when the computer key is hit to start and end the times is very large. So the estimate is not very accurate. A longer travel time would improve accuracy.

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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 attempted to hit the timer button when the object reached the half way point to measure time for the first half of travel vs the second half. The 2nd half was about twice as fast (half as long) as the first half but times are so small that it's hard to get any consistency. My best estimate of the average time for the first 14 cm of travel was 1.3 seconds and about .7 seconds for the last 14 cm of travel.

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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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35 minutes

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

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Excellent work. Be sure to see my note about the bead, etc..