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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June 12 around 12:30pm
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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:
On setting up this experiment I used my Physics book with an ISBN of 0130606200 that I use for this class. The object I used is the car that came with my lab materials that is about 7.3 cm’s long and 3 cm wide. I object that I propped the book up with was a cloths pin that is 1.3 cm’s high when laying flat, and was about .5 cm from the edge of the book on the bottom. The car did indeed roll smoothly down the book and I think the car did speed up a little bit and the car did not go in a straight line, it curved slightly.
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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 off all, the car was around 7.3 cm’s long and 3 cm’s wide. The close pin (prop) was about 1.3 cm’s tall. The car rolled an approximately 22 cm’s on every roll. On the first roll in the starting direction, I measured how many cm’s it took for the car to travel on the book, and how long to took as well. I believe I am accurate to .5 cm. Here are the measurements for the first roll: (the letters are different times I rolled the car in that direction)
a) 18.45313 – 19.875 interval: 1.421875
b) 78.5 – 79.83984 interval: 1.339844
c) 130.0117 – 131.4922 interval: 1.480464
For the second roll, I turned the book in the opposite direction of the starting position and rolled the car three times. Here are the measurements for the second roll:
a) 10.125 – 11.46875 interval: 1.34375
b) 41.17188 – 42.48047 interval: 1.308594
c) 75.50391 – 76.83203 interval: 1.328125
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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 the average, the car was moving at a rate of .062337 seconds per cm. I believe I am accurate to the limit of .5 cm’s, because the car was difficult to stop at the end of motion in order to measure where it stopped every time the roll happened. I divided 22 into every interval and got how many seconds per cm.
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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 at the beginning was moving around .09375 seconds per cm. The average speed was around .06463 seconds per cm. I think that the average speed, when it reached the lower end of the book, was greater than the average speed.
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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 cars initial speed: 0
The cars final speed: approx. .04125 seconds per cm
Change in speed: approx. .5253 second.
speeds are in cm / sec, not sec / cm (think about the fact that your car's speedometer reads miles / hour, not hours / mile)
change in speed wouldn't be measure in seconds, but in cm / second
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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:
As the car goes down the book I click the time at the beginning, around the middle of the ruler, and at the end, where the car stops. This will give me two intervals; one for the top half of the incline and the bottom half of the incline. I have done the experiment one more time to explain the measurements: The time from the start to around the middle was .78125 seconds and from around the middle to the end was .296875 seconds. So, by looking at the intervals alone you can tell that the car is speeding up by taking less time to get from one part to the next.
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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?
It took me around 45 minutes to complete this experiment.
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You may also include optional comments and/or questions.
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&#Good responses. See my notes and let me know if you have questions. &#