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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.
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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:
For this setup I used the toy car in the Labkit, a 1 inch three ringed binder, the TIMER program, a ruler that contained cm, and the textbook for Phy 231. The textbook was titled University Physics by Young and Freedman and its ISBN number was 978-0-321-50121-9. The 1 inch three ringed binder was used to prop the textbook up in order to create a slight incline. The toy car was place on top of the inclined portion of the textbook. When the toy car was released it seemed to roll smoothly, in a fairly straight line and it seemed to have sped up as it went down the incline.
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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 toy car was measured to be 6 cm long. The textbook was measured to be 28.3 cm long. The incline height was measured to be 1.5 cm. The bottom book, the part not inclined was measure to be 0 cm. The distance from the incline to the end of the book was 25.1 cm. When the toy car was placed onto the inclined portion of the textbook, the toy car’s initial position was 5.3 cm. The toy car was then released and once the toy car reached the end of the textbook the toy car’s final position was 28.3 cm. The total distance traveled by the toy car = final position – initial position. Therefore, the total distance traveled by the toy car is 28.3 cm – 5.3 = 23 cm. The time it took the toy car to travel from its initial position to its final position was measured three times using the TIMER program. The three times obtained were:
1st trial : 2.089844 seconds
2nd trial: 2.042969 seconds
3rd trial: 2.152344 seconds
The book and incline were then rotated 180 degrees. And the experiment was repeated:
The toy car was measured to be 6 cm long. The textbook was measured to be 28.3 cm long. The incline height was measured to be 1.5 cm. The bottom book, the part not inclined was measure to be 0 cm. The distance from the incline to the end of the book was 25.2 cm. When the toy car was placed onto the inclined portion of the textbook, the toy car’s initial position was 5.2 cm. The toy car was then released and once the toy car reached the end of the textbook the toy car’s final position was 28.3 cm. The total distance traveled by the toy car = final position – initial position. Therefore, the total distance traveled by the toy car is 28.3 cm – 5.2 = 23.1 cm. The time it took the toy car to travel from its initial position to its final position was measured three times using the TIMER program. The three times obtained were:
1st trial : 2.0625 seconds
2nd trial: 2.199219 seconds
3rd trial: 2.183594 seconds
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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:
In order to find how fast the object is moving, or the objects velocity, you must divide time by distance. In other word velocity = distance / time. First we need to find the average of the distance and speeds for the two parts of the experiment. The average distance traveled by the toy car is found by (23 cm + 23.1 cm) / 2 = (46.1 cm) / 2 = 23.05 cm. The average time it took the toy car to travel from its initial to final position is found by (2.089844 s + 2.042969 s + 2.152344 s + 2.0625 s + 2.199219 s + 2.183594 s) / 6 = (12.73047 s) / 6 = 2.121745 s. Based on these averages, the velocity of the toy car is 23.05 cm / 2.121745 s = 10.86369945 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 toy car was at rest. Therefore the toy car was moving at 0 cm /s at the beginning of the timed interval. Based on my previous calculation, the toy cars average speed during this interval was 0 cm/s. I think that the object was moving at a speed greater than the average speed calculated when it reached the lower end of the book.
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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 –tied with- change in speed from one end to the other
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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:
You can have three positions marked on the textbook. Each marked position indicates when you will mark the speed. The first mark is where the toy car will be released, and this is also the starting point. The second mark is halfway between the starting point and the ending point. The third mark is the ending point, where the toy cars final position is. Every time the toy car passes on of the mark the click to time event button on the TIMER program will be pressed. This way we will be the speed of the toy car at the beginning, middle, and end. If the car speed up then the time between middle and end will be greater then the time between beginning and middle. If the toy car is moving at a constant speed then the time between middle and end will be the same as the time between beginning and middle. If the toy car is slowing down then the time between beginning and middle will be greater then the time between middle and end. I set up the rest of the experiment the same way. I just added another marker in the middle of the distance traveled. I obtained the following data
Toy car: 6 cm long
Textbook: 28.3 cm long
Incline height: 1.5 cm
Bottom book, the part not inclined: 0 cm in height
Distance from incline to end of book: 25.0 cm
Toy car’s initial position: 5.0 cm
Toy car final position: 28.3 cm
Total distance traveled by toy car: = final position – initial position
Total distance traveled by toy car: 28.3 cm – 5.0 cm = 23.3 cm.
The time it took the toy car to travel from its initial position to its final position was measured three times using the TIMER program. The three times obtained were:
1st trial:
Beginning: 0 seconds
Time to go from Beginning to Middle: 1.261719 seconds
Time to go from Middle to End: 0.90625 seconds
2nd trial:
Beginning: 0 seconds
Time to go from Beginning to Middle: 1.542969 seconds
Time to go from Middle to End: 1 second
3rd trial:
Beginning: 0 seconds
Time to go from Beginning to Middle: 1.34375 seconds
Time to go from Middle to End: 0.8710938 seconds
All three trials show that the time between middle and end is less then the time between beginning and middle. Therefore, all three trials show that the toy car is speeding up as it moves from its initial to final position.
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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 an hour and a half
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You may also include optional comments and/or questions.
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&#Your work looks good. Let me know if you have any questions. &#