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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.
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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 set my experiment up using 6th Edition Physics by Giancloi (Hardcover). I propped the book at the end of one side using a stack of four quarters and rolled the Hot Wheels car (from the lab package) down the book. I had to use four quarters to prop the book up because any less than that kept the car from rolling smooth enough. With this setup the car began rolling at a very slow speed and rapidly increased in speed before reaching the end of the book. The car traveled in a straight line 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:
I measured the time it took the Hot Wheels Car to roll down the book setup as described above. The car traveled a distance of 20.8cm. I got this distance by subtracting the length of the car (7.5cm) from the length of the book (28.3cm). I did this because the car started at rest with its back end lined up with the book, while I stopped the timer when the very front of the car reached the end of the book. The highest end of the book measured 4.4cm while the shortest end was 3.8cm.
It took the car 2.2059, 2.3015, and 2.2165 seconds to cover the 20.8cm for the first 3 trials. After the book and supports where turned 180 degrees it took 2.0625, 2.21875, and 2.203125 seconds for the car to travel the same distance.
I believe the accuracy was measured to +-0.1 millimeters and 0.0001 seconds. I don’t think the seconds were recorded as accurately is due to human error. It would be hard to believe that I started the timer at the exact time the car started moving and stopped it exactly when the front of the car reached the end of the book.
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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:
When using the data after turning the experiment 180 degrees the average time it took the car to get down the ramp was (2.0625 + 2.21875 + 2.203125) / 3 = 2.1615 seconds
20.8cm was the distance traveled so 20.8cm/2.1615sec = 9.62cm/seconds this is the average speed.
I estimated the accuracy to 0.01cm/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:
The car started moving from zero so initially it was moving at 0cm/second. From observing the car travel down the ramp I can see that when it first started moving it was moving much slower than the average. When the car reached the end of the ramp It looked to be going the fastest.
The average speed was 9.62cm/second.
At the lower end of the book the car seemed to be travelling at the greatest speed. As the car went down the ramp the speed rapidly increased.
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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. I would think the tie would be between the object’s average speed and final speed. I believe the average speed I calculated is equal to the speed the car was traveling at the end of the book.
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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 setup my experiment in the same way as the one we did above. The only difference was I used five quarters instead of 4 to prop the Physics book up. I’m not sure why but the car wasn’t rolling as well this time when only using 4 quarters. I started the clock the moment I released the car and clocked the time when it moved pass 6.5cm, 13.5cm, and 20.5 cm. The times between these distances were 0.828125sec, 0.796875sec, and 0.640625sec. This supports my conclusion that the car is increasing speed as it heads down the ramp. Each of the distances were 7cm apart and the car moved faster through each point. If I was to try to really be accurate in the experiment I would do 3-4 trials to make sure this data is consistent. With the measurements I made the car was going the fastest at the end of the interval.
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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?
Around an hour
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You may also include optional comments and/or questions.
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self-critique #$&*
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&#This lab submission looks very good. Let me know if you have any questions. &#