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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 The Pharmacy Technician Fifth Edition (ISBN: 978-1-61731-070-6) book and the toy car from my lab materials packet to complete the following experiment, and to prop the book up I used two dominos stacked on top of one another placed horizontally. The object rolls smoothly, speeds up as it travels, and veers slightly to the right (viewpoint:from the bottom of the slope created by the book) as it travels down the book.
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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:
Time required for the toy car to go from rest at the top of the small incline to the end of the book. I stopped the timer each time the car hit the table after rolling down the incline so that the car had rolled the entire length of the book. I think the data is measured relatively accurately, especially the time trials for the car because I played around with the timer program and the car to make sure I was releasing the car from the same spot each time and that the results seemed to be in a consistent range.
Trial 1: 0.804
Trial 2: 0.828
Trial 3: 0.79 sec
Distance traveled: 7.90 in
Length of book:11 in
Length of car: 11-7.90in= 3.1 in
How high book is lifted: 0.45 in
Distance of end of book to supports (dominos): 9.5 in
Time trials with book turned 180 degrees:
Trial 1: 0.801 sec
Trial 2: 0.774 sec
Trial 3: 0.854 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:
avg velocity= change in position/change in time
=7.90in/.804 sec
=9.83in/sec
=7.9in/.828 sec
=9.54in/sec
=7.9in/.79 sec
=10 in/sec
An average of the above three velocities gives 9.79in/sec
Depending on how accurate my measurements and time trials were, would best determine how accurate the car’s average speed is. If the measurements I made are relatively accurate, then rounding to two decimal places for average velocity should give an accurate measure of the velocity of the toy car.
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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 timed trial, the object was at rest, the average speed during this interval is 9.79in/sec. I think that as the object approaches the end of the book, the book begins to level out more because it is not a hardback book. Therefore, although the car is traveling faster near the end of the book, if the book was longer, the car would begin to slow down as the incline decreased.
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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
The object began from rest, so the change in speed would be the greatest.
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Good, but since the object started from rest the final speed would equal the change in speed.
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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 determine if the object was speeding up or not I video taped the car as it moved in conduction with the timer on my cell phone. This way I was able to pause the video and see how much distance had been travel vs. how much time had passed and there was a larger avg speed as the object traveled about the second half of the book.
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That's a fairly reliable way to check your hypothesis. However there is no guarantee that the cell phone stops the frames at equal intervals.
There is no reason to expect that any unevenness in the intervals is greater for one half of the trial than for the other, so if this held up for a number of trials we could be quite confident in the conclusion.
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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?
This took me about 45 minutes
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You may also include optional comments and/or questions.
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Well done.
Check my notes.
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