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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submitted 1/25 10
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Take reasonable care to get good data in this experiment. Try to do the timing as accurately as possible. Measurements of length, height, etc. should be reasonably accurate (e.g., with a meter stick or ruler you can measure to withing +- 1 millimeter, but it's not necessary to try to determine fractions of a millimeter).
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).
• The book's cover should be straight and unbent.
• The object should roll fairly smoothly.
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.
• Using the TIMER program determine how long it takes the ball to roll from one end of the ramp to the other, when released from rest. Time the object's motion at least three times.
• Determine how far the object actually travels as it rolls from one end to the other.
• Determine how much higher one end of the book was than the other, and how far it is from one end to the other.
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 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?
Note: Never trust Web forms. 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. (However you should understand that if a Web form gives you a confirmation, then it has almost certainly worked correctly and sent the data to the appropriate file. It's still a good idea to keep a copy of the confirmation.)
your brief discussion/description/explanation:
While setting up this experiment, I chose to use a textbook as I am a middle school teacher. The book I chose is titled Agricultural Mechanics: Fundamentals and Applications. The author of the book is Ray V. Herron and the ISBN # is 1-4018-5956-9. It measures just under 4 cm in thickness with a width of 22cm.
The object chosen to travel down the incline was a spool of gray sewing thread. This thread was manufactured by Coats and Clark. The diameter of this spool of thread measure 3.8 cm. When being used as a prop, the pencil was placed so that it ran from left to right (horizontal) beneath the book. I did this to keep the book steady and prevent it from leaning at an angle towards any specific direction.
The object chosen to serve in propping up the book was a sharpened Mall of America pencil with multi colored stars and a green eraser. It has a width of 0.7cm.
When traveling down the incline the spool of thread traveled fairly straight, but veered off course slightly. It went from traveling in the center of the book and began to travel more to the right as it began to travel down. The spool of thread started to travel slowly, but then gradually picked up speed and was traveling faster.
My second trial which was conducted with the book turned 180 degrees went a little differently. It seemed like it took the spool of thread a little longer to get going and that it traveled slower than the first 3 trials. It also seemed to travel fairly straight, only veering off by less than 0.5 cm each time.
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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:
Measurements taken for this experiment included the length of the book and the height of the book while propped up. The length of the book measures 28.3 cm and the height of the book while propped up was a total of 4.6 cm. Other measurements taken include time from the six test trials for how long it took the spool of thread to roll down the ramp.
The times for the first three trials were as follows:
Trial 1- 2.140625 s
Trial 2- 2.21875 s
Trial 3 - 2.15625 s
The times for the second set of trials :
Second run, Trial 1- 2.75 s
Second run- Trail 2- 2.453125 s
Second run- Trial 3- 2.078125 s
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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:
To determine how fast the spool of thread was traveling, I took the distance traveled and divided it by the time it took the object to travel the length of the book. I had to determine an average for the times. To get an average I added up the times and then divided by the number of test runs per trial.
The average time of the first 3 trials was 2.171875.
The average time of the second 3 trials was 2.427083
To determine the average speed for the spool of thread, I took the length of the book (total distance traveled) and divided it by the average time it took to travel the distance.
For the first set of time trials, the average speed was 13 cm/s + .1cm
For the second set of time trials, the average speed was 11.7 cm/s + .1cm
I believe that I was accurate enough to determine the average speed of the object to + .1cm. This is based upon the fact that there could be differences between my measuring devices to others.
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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 collect data to prove that the object (spool of thread) was indeed speeding up, I measured to the center of the book and placed a pink post it note to indicate the center.
While running test trials, I used the time function to start timing when the object rolled to the center of the book, clicked the time to take a time measurement and then clicked the timer again to find out how long it took to get from the mid point to the end. The average for the time trials was found and then the length for the center (around 14.1cm) was divided by the average time to determine how many cm the spool of thread was traveling per second. If the spool of thread travels more cm during the second set of collected data it shows that the spool of thread does in fact speed up.
Based on my experiment, I collected the following data:
Trail 1: Time to reach mid point -1.046871s
Time to go from mid point to end-.515625s
Trail 2: Time to reach mid point -1.09375 s
Time to go from mid point to end- .640625 s
Trail 3: Time to reach mid point -1.265625 s
Time to go from mid point to end- .515625 s
The average speed for the first half: 12.5 cm/s
The average speed for the second half: 25.4 cm/s
When looking at my average speeds it does not seem as though my results are accurate, but it does seem to show that the object is speeding up. Were there multiple ways to measure this data and if so, which is the best way???
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?
Around 1 hour and 15 minutes or so
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You may also include optional comments and/or questions.
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Please copy your document into the box below and submit.
&#Very good responses. Let me know if you have questions. &#