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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 a standard composition notebook for the ramp with a can of pepsi that you would find from a vending machine
as the object to roll down the incline. it took 1.97 seconds to roll to the right
and 1.85 seconds to roll to the left when on the table. it was propped up by a stack of 3 quarters. the can rolled very smoothly and sped up untill it hit the table, but from the time i released the can till it was at the end of the book it was gaining speed.
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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 part of the book that was used for the experiment was 29cm long, the can was a full 12oz can of pepsi the book was propped up by 3 quarters,
average of 1.97 seconds to roll to the right and 1.85 seconds to roll the other way to the left. the experiment was all done on top a flat table.
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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:
on average it was moving 14.72cm per seconds to the right and 15.67cm to the left when reversed. that was the over distance by the total time. this speed would be different if you pick the middle of the time or the middle of the distance. but given the short time that it rolled and having to click the timer at exactly the right moment i think this is a pretty good estimate of the average speed.
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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 begining the can was moving slower because it started from a complete rest. by the end of the book it was at its fastest speed and was higher than both the average and the begining of the test.
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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:
the initail speed would be zero since this is the time you listed as first clicking the timmer and it being released so this would be the slowest. then would be its average speed of 1.97 and 1.85. next would be its fastes speed right before
it reaches the end of the book. the change in speed would be increasing from start to finish
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You don't have units on 1.96 and 1.85. However those look like your time intervals, not your average speeds.
How would you get average speeds from your data?
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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:
for this test i timed the can rolling from half way doen the book to the end and timed it. if the can does speed up then this time, compared with the first test, should be different. if i cut the time in half from the first test where the can rolls down the entire incline then it should match the time of the can starting to roll doen from half way but they dont. the can starting half way takes longer which indicates the can does in fact speed up.
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Good.
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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 mins
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You may also include optional comments and/or questions.
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Check my note on your average speeds. They don't seem to be correct.
Otherwise good work.
&#Please see my notes and submit a copy of this document with revisions, comments and/or questions, and mark your insertions with &&&& (please mark each insertion at the beginning and at the end).
Be sure to include the entire document, including my notes. &#
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