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

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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I started by useing my physics book entitled Physics Giancoli.I used an empty 20oz. Mountain Dew bottle. It was completely empty.I used a black 3 ring binder notebook to prop up the ends of the physics book and proped it up 2 1/4 inches up.The object rolled well. It took just a second or so to get moving, but once it did it picked up speed. I also rolled in a very 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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time data from the timer program

1st roll - 450.4414 451.4961

2nd roll - 483.2266 484.6367

3rd roll - 522.571 524.0

time data after flipping the book 180 degrees

1st roll - 667.2773 668.5547

2nd roll - 705.7813 707.043

3rd roll - 736.8594 7380859

the length the bottle rolled was exactly 11 inches

the book was proped up at one end by 2 1/4 inches higher than the other

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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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I would say on average the speed the bottle rolled was around 1.7 and 2 seconds from the top to bottom of book. I think I can say this by looking at the numerical data I obtained using the timer program.

It looks to me like the average time required for the roll is a bit less than you say here, more like 1.3 s or 1.4 s.

You need to calculate and report the duration of the time intervals; alternatively you can just report them directly from the third column of the Timer output.

Then you should average the reported time intervals.

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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 done this by lowering the height on which the book was propped. I propped it up on 1/2 inches and released the bottle. The data I received using the timer program is as follows:

1st roll-1481.762 1483.895

I then switched 180 degrees and repeated the roll as got the following:

1st roll-1524.707 1526.9773

On both rolls the bottle started very slowly then picked up speed quickly. This proves that the bottle will always gain speed no matter how high the incline.

You don't appear to have measured anything to support this conclusion. You are reporting what you think you saw (and what I'm sure you did in fact see, since this is exactly what is expected). However it is easy to fool the eye (though not really so in this case) and we need hard data, not fallible perceptions to justify our conclusions.

Figure out what you need to measure in order to justify your conclusion. Then report your measurements and show that they justify your conclusion.

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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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46 min

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

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Good data, but you need to report the durations of your time intervals, not just the clock times at the beginning and end of each (though these do appear to be both reasonable and consistent, and I expect that they are acc urate).

'gr99