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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 **
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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, 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:
I used my textbook titled Chemistry, isbn: 9780547125329
The object is a small wooden cylinder, and the book is being propped up by 3 quarters. The object rolls straight and speeds up as it rolls down.
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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 distance from the end of the book where the cylinder is placed to the other end of the book is 26.5 cm.
The quarters are placed 2 cm underneath one end of the book. The propped up side of the book is 4.8 cm and the other end resting on the table has a height
of 4 cm.
Time 1 = 2.768 s Time 2 = 2.628 s Time 3 = 3.084 s
Average Time = 2.833 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:
velocity = 26.5 cm / 2.833 s = 9.35 cm/s
I believe this result is reasonably accurate because the average of the 3 times that I used is a good indication of how fast the object moves. The object
takes a little bit to get started moving, and this accounts for some of the variation in times.
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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 the beginning of the time interval, the object was at rest. The average speed during the time interval is 9.35 cm/s. The object was moving at a greater
speed than average when it reached the lower end of the book.
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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, average speed, final speed & change in speed tied.
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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 divided the length of the book in thirds, placing a line at each third. I then started the object rolling, and clicked the timer at the two points and
then a third time as it fell off the end. This gave me the time intervals between the starting position and the first third of the book, between the 1st and
2nd thirds, and then between the last third and the end of the book. My results for these time intervals are as follows: At point 1: 1.826 s, point 2:
0.652 s, final: 0.523 s. This clearly shows that the object is speeding up as it rolls down the book because the time intervals are decreasing.
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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?
1.5 hours
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You may also include optional comments and/or questions.
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&#Your work looks good. Let me know if you have any questions. &#