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Phy 121
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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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:
I used my Introductory Chemistry Book 3rd edition 2009. The ISBN is 978-0-13-600382-3. The object I used was a can of Spaghettios and it was full. I used 4 quarters on
two corners of the book to prop it on. The object rolled smoothly, the speed increased, and it rolled in a striaght line in one direction. I laid the book on a flat table.
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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:
I measured the length, width, height of the book, and height of the book proped up on four quarters. The measurements of the book included 282mm or 28.3cm (length), 214mm or 21.4cm (width), 30mm or 3.0cm (height of book), and 40mm or 4.0cm (height of proped book). The measurements I took next was the width and length of the spaghetti can. The width was 75mm or 7.5cm and the length was 112mm or 11.2cm. I measured these measurements with a ruler using the centimeter side as I also reported the measurements in millimeters also. I believe the measurements were recorded accurately.
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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:
I took the length of the book which is 28.2 cm and divided it by the number of seconds it took to travel from one end of the book to the other. So I took 28.2/2.96 and I got 9.53cm/sec on the first trial, 9.62cm/sec on the second trial, and 10.97cm/sec on the third trial. On average it took 10cm/sec the original way. Then when I moved the book 180 degrees it took 12.76cm/sec on the first trial, 9.53cm/sec on the second trial, and 9.72cm/sec on the third trial. On average it took 10.48cm/sec. I think my estimate is acurate because the book is 28.2 cm long and it took around 2.96 seconds to complete so you just divide those and it would tell you the number of cm it travels in one second.
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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 interval it was moving around 9.53cm/sec. The average speed was not during this interval. I think the object was moving at a speed less than the average speed when it reached the lower end of the book because the slope was not as steep as the upper portion 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:
Its final speed, the change in its speed as it rolled from one end of the book to the other, its average speed, the objects initial 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:
You could set the experiment the same way as before and just time the object how long it takes to get the middle of the book and then again from the middle to the end of the book and the results should show that it takes less time to roll the second half of the book compared to reaching the middle of the book from the starting position. Then you could determine the speeds by measuring the legnth from the top to the middle of the book and then from the middle to the end of the book. Then you would divide the length by the time and it would show you that the time it takes to get to the end from the middle of the book is faster than the top to the middle. The results would be (14.1cm/1.074sec) 13.13cm/sec for the first half and (14.1cm/0.656sec) 21.34cm/sec for the second half. With this it concluded that the can does speed up as it rolls down the incline.
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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?
25 minutes
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&#Your work looks very good. Let me know if you have any questions. &#