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.
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, 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 on the Assignments page).
The book's cover should be straight and unbent.
The 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.
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. Time the object's motion at least three
times.
Determine how far the object actually travels as it rolls from one end to the other.
Determine how much higher one end of the book was than the other, and how far it is from one end to the other.
Then reverse the direction of the book on the tabletop, rotating the book and its prop 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?
Note: Never trust Web forms. Compose your answer in Notepad or a word processor, saving it every few minutes, then copy and paste it into the box. Power could surge, your
computer could malfunction, in any of a number of ways the work you put into this form could be lost. Compose it elsewhere and keep a copy. (However you should understand that
if a Web form gives you a confirmation, then it has almost certainly worked correctly and sent the data to the appropriate file. It's still a good idea to keep a copy of the
confirmation.)
your brief discussion/description/explanation:
I am using an empty Pepsi can, the book entitled Science Explorer Grade Six Teacher's Edition(ISBN: 0-13-190231-8), and a thin notepad .04 cm thick. The book is 28.2 cm long
and approx. 3.3 cm thick. It did seem to roll in a straight line and sped up closer to the end.
First roll - 2.45 sec.
Second - 2.69 sec.
Third - 2.50 sec.
28
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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:
First roll - 2.45 sec.
Second - 2.69 sec.
Third - 2.50 sec.
I managed the timer and my husband released the Pepsi can at the same or close to the same start position on the book each time. He placed his opposite hand at the end of the
book and when the Pepsi can hit his finger, he said stop for me to stop the timer. No this is not perfectly accurate due to two people's response times involved.
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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:
28.2cm/2.45 sec = 11.51cm/sec
28.2 cm/2.69 sec = 10.48cm/sec
28.2 cm/2.50 sec = 11.28cm/sec
When I add up the three calculations and then divide by 3 to get the average, the answer is 11.09 cm/sec. I don't believe that this is extremely accurate just due to the range
of speeds and just human response time. It is probably accurate within 1/2 sec.
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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 put a piece of tape at about the halfway point of the book 14.1 cm. We timed the Pepsi can from the starting point to this point 3 times and also timed the Pepsi can from the
middle point to the end 3 times and compared the speeds.
Top to mid point time - 1. 1.59 seconds, 2. 1.43 seconds, 3. 1.5 seconds
Mid point to bottom of book - 1. .69 seconds, 2. .37 seconds, 3. .89 seconds
Of course human error and response times are involved again, but the item is definitely speeding up based on this data.
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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?
about 45 minutes
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You may also include optional comments and/or questions.
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Please copy your document into the box below and submit.
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Revised: 23 Jan 2010 13:30:17 -0500
&#Your work looks very good. Let me know if you have any questions. &#