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PHY 231
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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8/14 13:56
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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 within +- 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:
Organic Chemistry ISBN:978-0-495-11258-7
Object: Hot wheels army truck!
Prop: A very thin notebook with a magnet on top of that.
The object definitely started much slower at a creeping pace but picked up very quickly. The direction stayed in a straight path.
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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:
The amount of time in seconds was measured from the release point of the toy truck to the end of the book (placed beside a wall) where the front of the truck made contact with the wall. This distance was 26 cm - 5cm (the length of the truck); therefore, the total distance traveled was 21 cm. The prop height was approximately 1.1 cm. The prop to book end was 20 cm. (Didnt realize how important this was until I turned it 180 and was way off my #s at first - realized it was this and adjusted for the 2nd set.)
Seconds from beginning to end.
2.246094
2.183594
2.167969
2.339844
2.230469
2.058594
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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:
Average time = 2.204427 s
Average Speed = 21 cm / 2.204427s = 9.5 cm/s
I believe I was able to accurately measure the book and hot wheels toy very accurately simply based on the designed size. The speed would be accurate to the second for sure and I feel as though the average was accurate including the tenth of a second. My answer is given as 9.5 cm/s because anything past this amount would be pure speculation due to human error.
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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:
I started the object at a zero velocity. The average speed at the top of the slope was much slower; however, the problem did not ask us to record intervals of each run; therefore I do not know for sure in regard to the above data. I took one measure as a sample and it showed the 1st half of the slope as 1.417 s and the 2nd half as .734. My conclusions support the idea that the truck was going faster at the end.
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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:
Initial speed - Zero (cm/s)
Change in speed - Change in Velocity / Change in Time (cm/s^2) - Different units being measured.
Average speed - Distance traveled/Change in time (cm/s)
Final speed (x1) - The fastest speed. (cm/s)
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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:
As stated above I set up the same ramp/slope with a line midway down the book from the front of the trucks starting position. (Worked out to be 10.5 cm) Then, I clicked the timer at the mid-line as well as the end of the book.
Total time - 2.151 s
1st half of the slope as 1.417 s and the 2nd half as .734s.
This shows a majority of the time spent was on the 1st half of the slope and velocity got greater as it continued down the slope.
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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.
OK
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&#Very good data and responses. Let me know if you have questions. &#