initial timing experiment

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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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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The book used was titled NATURAL WONDERS - READERS DIGEST EXPLORE AMERICA (ISBN 0-89577-904-8). The object used was a tube of Blistex chapstick. The objects used to prop up the book were 4 quarters, that is two stacked on top of each other under each side of the book.

The object rolled very smoothly and followed a fairly straight path from top to bottom, varying approximately 1 cm on some trials. The book was raised 3 mm higher on one end, as this is the thickness of each pair of quarters.

The object seemed to speed up as it reached the end of the book.

Book length - 281 mm

Object travels about 275 mm (I could not start it from the very top of the book of course)

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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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In the following trials the cylinder was released at the top of the book and observed rolling down the incline to the end of the book. When the cylinder was released the timer was started. When the cylinder left the end of the book the timer was stopped. Since some of the data on the timer program was displayed to the hundredth of a second, all recorded data has been rounded to the nearest hundredth of a second.

The following tables represent the time in seconds it took the cylinder to travel the distance down the book. Table 2 gives data for the same experiment only the book and its props have been turned 180 degrees.

All data was attempted to be measured as accurately as possible.

Distance traveled by cylinder - about 275 mm

Table #1:

Trial 1. 2.39 seconds

2. 2.38 seconds

3. 2.28 seconds

4. 2.16 seconds

5. 2.25 seconds

Rotated 180 degrees

Table #2

Trial 1. 2.46 seconds

2. 2.56 seconds

3. 2.34 seconds

4. 2.47 seconds

5. 2.53 seconds

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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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Average of Table 1 = 2.29 seconds

Average of Table 2 = 2.47 seconds

For Table 1:

d=rt

275=R(2.29)

275/2.29 = 120 mm per second or 12 cm per second

For Table 2:

d=rt

275=R(2.47)

275/2.47 = 111 mm per second or 11.1 cm per second

The average of the two speeds is about 11.6 cm per second.

Obviously when the book was turned 180 degrees, the cylinder traveled more slowly. This more than likely is due to how level the surface is the experiment took place on.

I believe I was able to determine the accuracy of the objects average speed within +/- 1 cm per second. The surface was not perfectly level and the distance traveled by the object varied by a small amount each time.

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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 determine for sure whether or not the object is speeding up as it rolls down the incline, several measurements were taken at specific points on the book. At 75, 150, and 250 mm from the top of the book where the object is released, markers have been placed. Times will be recorded on the intervals from release to 75mm, 75mm to 150mm, and 150mm to 250mm.

Interval 1 is from the release point to the 75mm mark, Interval 2 is from the 75mm mark to the 150mm mark, and Interval 3 is from the 150mm mark to the 250mm mark.

TABLE 3

Trial 1

I1 0.98 seconds

I2 0.57 seconds

I3 0.45 seconds

Trial 2

I1 0.98 seconds

I2 0.52 seconds

I3 0.50 seconds

Trial 3

I1 0.95 seconds

I2 0.59 seconds

I3 0.45 seconds

All of these times indicate how long it took the object to travel 75 mm in the indicated interval.

Averages:

I1. 0.97 sec

I2. 0.56 sec

I3. 0.47 sec

Average Speed per Interval:

I1. 77 mm per second

I2. 134 mm per second

I3. 160 mm per second

The data show that the object's speed increased as it rolled down the book.

To obtain more accurate data, it would be better to have used a longer book, or possibly a long piece of wood. This would allow greater interval spans and also a greater period of time for the object of roll down the incline and increase its speed.

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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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1 hr 45 min

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

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Excellent report.