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Phy 231
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.
** Initial Timing Experiment_labelMessages **
If the format is not satisfactory, please let me know so that i can send in my original file.
Thanks,
Isaac
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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:
Book used - College Physics ISBN 0131495798
Object used - Regular marble with a diameter of 1.5 cm +-1mm
Propped up with 6 pennies stacked 2 X 2, 2 sets for corners, and one for center
Ramp - Composed of two plastic 30 cm rulers sided by side with marble rolling down center. Ruler ramp was held in place by 4 thumbtacks pushed into College physics book (old book but smooth) at corners.
Procedure - Marble was pushed the incline with a domino to an initial start point of 0 cm in between the ruler ramp, it was then released and the timer initiated at the same instant, it rolled down the ramp and hit a towel cushion at the end of the 30 cm, (a piece of the towel stopped the marble at this point), and the timer stopped at this same instant.
Sometimes the marble bounced or rocked in the beginning of the roll, but rolled down uniformly after a few oscillations.
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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:
Marble was pushed the incline with a domino to an initial start point of 0 cm in between the ruler ramp, it was then released by removing the domino and allowed to roll down the ruler ramp, the timer was initiated at the same instant. It rolled down the ramp and hit a towel cushion at the end of the 30 cm, (a piece of the towel stopped the marble at this point), and the timer was stopped at this same instant. Data for both runs is as follows for time to roll 30 cm.
Delta Time Run 1 in seconds (Runtimes in sequential order)
3.699219
3.130859
3.021484
3.630859
3.021484
3.742188
Delta Time Run 2 in seconds (Runtimes in sequential order)
3.349609
3.419922
3.269531
3.050781
3.419922
3.351563
Accuracy was effected by the users ability to gauge when the marble finished its run down the ramp. Timer clicks was particularly affected.
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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:
Time Average of first 6 runs = (Run 1 + Run 2 + Run 3 + Run 4 + Run 5 + Run 6) / number of runs
Time Average = (3.699219 sec + 3.130859 sec + 3.021484 sec + 3.630859 sec + 3.021484 sec + 3.742188 sec ) / 6 runs
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You didn't need to type out
(3.699219 sec + 3.130859 sec + 3.021484 sec + 3.630859 sec + 3.021484 sec + 3.742188 sec ) / 6
It would have been sufficient to say that you calculated the mean of the six times, as you pretty much have in the next line.
Also your timing is not accurate to 7 significant figures, so most of the figures you are reporting are irrelevant. At best your timings are good to the hundredth of a second.************
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Time Average first = 3.743488 seconds / run
Time Average of Second 6 runs = (Run 1 + Run 2 + Run 3 + Run 4 + Run 5 + Run 6) / number of runs
Time Average = (3.349609 sec + 3.419922 sec + 3.269531 sec + 3.050781 sec + 3.419922 sec + 3.351563 sec) / 6 runs
Time average second = 3.310221 second / run
Average speed first six runs = distance / first average time = 30.0 cm / 3.743488 sec = 8.90 cm / sec
Average speed second six runs = disance / second average time = 30.0 cm / 3.310221 sec = 9.06 cm / sec
It was a little tough to click the release and stop times at a synchronized time, this probably effected the average time.
I think that My measurements can be estimated to be accurate to about +-0.5 seconds.
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I think you're more accurate than that, perhaps to within +- 0.1 second, though that's pushing it.
In any case, given these limits on your accuracy, your velocities should probably be rounded to the nearest .1 cm/s.************
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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 timed interval the object was at rest, so had a velocity of 0.
Average speed in the interval for all runs combined would be as follows
Avg Speed All Runs = (Average Speed 1 + Average Speed 2 ) / 2 = (8.90 cm / sec + 9.06 cm / sec) / 2 = 8.98 cm / sec
The Object at the lower end of the Ramp was moving at a greater speed then I calculated.
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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:
Speed in order from least to greatest.
Initial Speed
Average Speed = Change In Speed
Final Speed
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The change in speed is the difference between the initial and final speeds.
Since the initial speed is zero, the change in speed is equal to the final speed.
This is greater than the average 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:
I constructed a ramp from a book and two rulers. I laid the book on a level flat surface, and place two rulers with a decreasing angle at the edges sided by side on that book. I tacked the two rulers in place on the book, and made the 0 cm mark my release point. I propped up the one of the ends of the book with 6 pennies stacked 2X2, on the corners and center
to give it a rise of about 2 mm.
A marble was then pushed up the ramp with a domino to a common starting point and released from rest and allowed to accelerate down the ramp 30 cm. the release and stop times were recorded, six times one way, then the book was flipped around 180 degrees, with the corner stacks of pennies also switched, and the process was again followed 6 more times.
Final average speed was determined by first finding the average time of the first six runs with data as follows:
Time Average of first 6 runs = (Run 1 + Run 2 + Run 3 + Run 4 + Run 5 + Run 6) / number of runs
Time Average = (3.699219 sec + 3.130859 sec + 3.021484 sec + 3.630859 sec + 3.021484 sec + 3.742188 sec ) / 6 runs
Time Average first = 3.743488 seconds / run
And the second set of runs with data as follows
Time Average of Second 6 runs = (Run 1 + Run 2 + Run 3 + Run 4 + Run 5 + Run 6) / number of runs
Time Average = (3.349609 sec + 3.419922 sec + 3.269531 sec + 3.050781 sec + 3.419922 sec + 3.351563 sec) / 6 runs
Time average second = 3.310221 second / run
From the information above average speed was calculated as follows:
Average speed first six runs = distance / first average time = 30.0 cm / 3.743488 sec = 8.90 cm / sec
Average speed second six runs = distance / second average time = 30.0 cm / 3.310221 sec = 9.06 cm / sec
Then all the data was summed and the average speed of all runs was calculated as follows:
Avg Speed All Runs = (Average Speed 1 + Average Speed 2 ) / 2 = (8.90 cm / sec + 9.06 cm / sec) / 2 = 8.98 cm / sec
Final Average Speed = 8.98 cm / sec
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This is well done, but it doesn't answer the question of whether the marble was gaining speed.
A typical experiment to address the question would be to time the marble down the first half of the ramp, and down the entire ramp. The data could then be used to establish that the marble is indeed moving faster on the second half.************
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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?
With trial and error it took about 3 hours to complete this in total time. But once I had a reliable model built, The time to complete this lab, including typing time was about 45 minutes. Finding a hard suitable surface was the first issue, a glass desk was not a good surface when the experiment was rotated 180 degrees. Time for the marble to for down the ramp was decreased by about a whole second.
Using a textbook without a guide rails also complicated the measurements Kind of like a drop of water going down the back of a hand, it just went all over the place.
After a break and some thinking,(slept on it after the first go) a solid ramp was devised as indicated in my report. It was found that not touching the marble with my hands helped get the measuring times closer, and the experiment was conducted on my kitchen floor, where the tiles were utilized to indicate proper ramp prop up spots.
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You may also include optional comments and/or questions
Good Lab, It was fun to construct something that worked so well.
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Revised: 06 Aug 2012 00:00:48 -0400
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&#Good responses on this lab exercise. See my notes and let me know if you have questions.
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