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Phy201
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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8/31 12pm
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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.
wdThen 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 used is my Physics 201 textbook, Giancoli, sixth edition. I used the matchbox car included in the lab kit to perform this experiment. I chose one domino to prop my book up at one end. It rolled just fine, started off slow, and gradually accelerated speed as it moved towards the end. It also rolled completely in a straight line to the finish line or endpoint.
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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:
So, starting off positioning my book in the original position, I recorded the following:
Total Distance Covered = 11 inches to reach finish line.
Time to reach finish line = 2.27, 2.26, 2.28 seconds (3 recordings)
The book was raised precisely 0.5 inches high, by means of the domino.
Distance from the domino to the end of the book touching the table was 10.5 inches.
Rotating book and configuring same set up, all remained the same, except time to cover distance. It was recorded as approximately 2.21, 2.29, 2.29 seconds (3 recordings) to reach the endpoint.
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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:
Total Distance / Total Time = 11 inches* intervals / 2.27 + 2.26 +2.27 + 2.21 + 2.29 + 2.29= 66 Total Inches / 13.59 total seconds = 4.9 inches per second
I totaled the distance traveled during all recorded intervals divided by total time recorded during all intervals.
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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:
In accordance with my previous calculation, the average speed was 4.9 inches per second.
I believe that the matchbox car was moving at a greater than average speed when it reached the lower end of the book. Not only through common observation, but given the degree of slope, it would have accelerated with distance on the incline.
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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 – change in speed’ < final 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:
In order to confirm whether or not the object is speeding up as it rolls down the incline, I set up an experiment similar to previous. Instead, this time, I used a hard piece of cardboard, raised 2.5 inches on one end, and the distance from the smaller box supporting the higher end to the end touching the surface is 19 inches. I made this platform longer, so that I can divide the incline into two different intervals, recording times reaching midpoint and endpoint.
The total length traveled by the matchbox car was accurately 20 inches, at two intervals of 10 inches each.
The matchbox car reached the midpoint of 10 inches traveled at an average:
16.7 inches per second (10 + 10 + 10 inches / 1.8 seconds = 16.7 inch per second)
The matchbox car reached the endpoint of the second 10 inch interval at an average:
27.3 inches per second (10 + 10 + 10 inches / 1.1 seconds = 27.3 inches per second)
The data confirms that the object picked up speed as it got closer towards the endpoint, and nearly twice the speed compared to speed reaching midpoint.
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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?
It took me approximately 1 hour and 20 minutes to complete this experiment.
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You may also include optional comments and/or questions.
In accordance with the following question:
How fast was the object moving at the beginning of the timed interval?
Would this be calculated through separating the total length through segments as well, or some particular formula, can’t seem to locate it, or perhaps I am misinterpreting the question.
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