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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.
** Initial Timing Experiment_labelMessages **
5/28/2012 4:00
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Samantha Rogers
PHY 201
Initial Timing Experiment
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Note: The majority of student report taking less than an hour on this experiment, though a few report significantly longer times.
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, the toy car that came in your lab materials package (or, if you do not yet have the package, 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, which is also given on the Assignments page).
• The book's cover should be straight and unbent.
• The toy car (or other 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. For a typical book, a stack of two or three quarters placed under one end works well.
• 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. Once you've got the book set up, it takes only a few seconds to do a timing, so it won't take you long to time the object's motion at least three times.
• Determine how far the object travels as it rolls from its initial position (where you first click the timer) to its final position (where you click at the end of the interval). This will probably be a bit less than the length of the book, due to the length of the object itself.
• Determine how much higher one end of the book was than the other, and how far it is from the supports (e.g., the stack of quarters, or whatever you used to support one end) to the end of the book which rests on the table.
Then reverse the direction of the book on the tabletop, rotating the book an its supports (e.g., the stack of quarters) 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?
your brief discussion/description/explanation:
The book being used is the sixth edition Physics by Giancoli, with an ISBN number of 0130606200. The object beaching used is a roll of black sewing thread. I am using a stack of post it notes that is 2.4 cm hight to prop up the text book. The roll of sewing thread rolled down the text book very smoothly. The sewing thread speed up the further it was from the starting point and it also rolled in a very straight line.
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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:
1 3.952 3.952
2 4.819 0.867
1 1.768 1.768
2 2.66 0.892
1 1.341 1.341
2 2.302 0.961
1 4.395 4.395
2 5.461 1.066
1 1.771 1.771
2 2.73 0.96
1 1.809 1.809
2 2.801 0.992
What was measured was the time it took for the sewing thread to get from point A of the higher end of the book, to point B of the lower end of the book. This distance was 27 cm. I believe that the measurements are fairly accurate. The measurements were:
Roll 1: 0.867 sec
Roll 2: 0.892 sec
Roll 3: 0.961 sec
Roll 4: 1.066 sec
Roll 5: 0.96 sec
Roll 6: 0.992 sec
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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:
.867+.892+.961+1.066+.96+.992=5.738/6=0.956sec
Average velocity= 27cm/.956sec= 28.243 cm / second = average velocity
My estimation for how accurately I believe I was able to determine the objects average speed is +/- 0.01sec. The best reason for this is because I was able to start the timer exactly when I let go of the object and approximately stop the timer around the exact same point on the textbook.
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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:
At beginning of the timed interval the object was not moving exceedingly fast. According to my previous calculation the average speed during this interval was 28.243cm/sec. I think the object was moving at a speed greater then I calculated because as the object traveled down the slope the object picked up speed. So at the beginning of the distance traveled the object was moving much slower then when I stopped the timer.
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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:
Least:
- Initial Speed
- Change in Speed
- Average Speed
- Final Speed
Greatest
I think this is the correct order because the initial speed is very slow. The change in the speed will be greater but not as great as the average speed because the average speed includes both the slowest and the fastest speed, making the average speed a little higher then the change. The final speed is the greatest because as it travels down the slope it picks up more and more momentum.
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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:
I designed my experiment with two places on the textbook to measure the time it takes to get to that point (each point being the same distance of 13.5 cm). The fist point is half way down the traveled distance (Point A) and the second point is the final distance (Point B). I then recorded the time it took to get from the initial starting point to Point A 4 different times. Next, I recorded the time it took to get form Point A to Point B 4 different times. After recording all the data I found the average velocity that it took to get to Point A and from Point A to Point B. Finally I compared the velocity from Point A to the velocity from Point A to Point B.
Time Taken to get from initial point to Point A:
Roll 1: 0.831 sec
Roll 2: 0.803 sec
Roll 3: 0.754 sec
Roll 4: 0.781 sec
.831+.803+.754+.781=3.169/4=0.79225 sec
13.5 cm / 0.79225 sec = 17.040cm/sec=average velocity SLOWER
Time Taken to get to from Point A to Point B:
Roll 1: 0.252 sec
Roll 2: 0.280 sec
Roll 3: 0.234 sec
Roll 4: 0.306 sec
.252+.28+.234+.306=1.072/4=.268 sec
13.5 cm / 0.268 sec = 50.373cm/sec=average velocity FASTER
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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?
45 minutes
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You may also include optional comments and/or questions.
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&#Good responses. Let me know if you have questions. &#