initial timing experiment

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Phy 201

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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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 can of vegetables (full or empty; should be specified) or a jar (again full or empty); anything round and smooth that will upon release roll fairly slowly down the incline), 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?

your brief discussion/description/explanation:

I used the Physics by:Giancoli 6ed for my book (ISBN:0-13-060620-0). I used a regular sized 0.15oz tube of chapstick that was still full, never used. I used my droid incredible cell phone to prop the book up. The object rolled smoothly in the first trial, it rolled faste down the book and did not change directions. In the second run however once I turned the book around it was a little harder to get the stick to start rolling but once it did it rolled smooth and straight.

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In the space indicated 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 identify any patterns or trends.

your brief discussion/description/explanation:

I timed the experiment with the timer software which I believe to be pretty accurate.

First run with the book propped up on the right:

1 76.04688 76.04688

2 77.45313 1.40625

3 83.38281 5.929688

4 84.71875 1.335938

5 88.47656 3.757813

6 90.08594 1.609375

Using this data, I can extrapolate to see that the first run (data point 2) took 1.40625 seconds. The second run took 1.335938 seconds and the third run took 1.609375 seconds. The average of this time therefore is 1.45052 seconds.

Second Run with the book propped up on the left:

1 759.6094 759.6094

2 761.4063 1.796875

3 764.5703 3.164063

4 766.1172 1.546875

5 768.8281 2.710938

6 771 2.171875

Using this data, I can see that the first run took 1.796875 seconds, the second took 1.546875 and the third took 2.171875 seconds. The average time therefore was 1.838541 seconds.

Distance traveled: 28.4cm

Other dimensions: The book was propped up on a cell phone about 1.5cm high, the book itself is 3.5cm thick and the end of the book is 28.6cm from the cellphone.

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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.

your brief discussion/description/explanation:

In the first run, the tube was moving at approximately 19.6 cm/sec. In the second run the tube was moving at approximately 15.5cm/sec. Therefore the average of these two runs was 17.6cm/s. I estimate this accuracy by about plus or minus 4cm/sec because without more trial runs I am unable to get a better estimate or average and since there is a large discrepancy between my original trial runs I would say that this is the best estimate for accuracy I can get for now.

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How fast was the object moving at the beginning of the timed interval?

According to your previous calculation, what was its average speed during this interval?

Do you think the object, when it reached the lower end of the book, was moving at a speed greater or less than the average speed you calculated?

your brief discussion/description/explanation:

Initially the tube was moving at only 13.6cm per second whereas the average speed was approximately 17.6cm per second (average of 15.5 cm/s and 19.6cm/s). I think that the tube was rolling faster at the bottom of the book.

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List the following in order, from least to greatest. Indicate 'ties': The object's initial speed, its final speed, its average speed, and the change in its speed as it rolled from one end of the book to the other.

your brief discussion/description/explanation:

The change in speed while rolling from one end to the other was probably the least amount because it was probably only a change of about 4 or 5 cm/s. Then the next smallest is the objects initial speed followed by its average speed and then lastly its final speed.

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Devise and conduct 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.

your brief discussion/description/explanation:

To prove that the object was speeding up I would have the same set up as in this experiment with the book, the tube and the phone probs but I would have a paper ruler taped to the book for easy measuring when I time how long it takes for the tube to reach different distances along the book. Then I would graph this data to find that it would produce an increasing curve showing that the tube speeds up as it rolls down the book.

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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:

Approximately how long did it take you to complete this experiment?

30min

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You may also include optional comments and/or questions.

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&#Very good data and responses. Let me know if you have questions. &#