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PHY201
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 **
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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:
I used a book that was 28.5 x 22 x 1 cm in dimension. I used a marble that had a diameter of 1.2 cm. I used 5 quarters to stack under the book for a total additional height of 8.75mm. With the book raised to my right the marble rolled diagonally towards me. With the book raised to my left the marble rolled diagonally away from me. The marble speeded up as time passed. The marble didn’t follow a straight line probably due to the book not being perfectly smooth or the quarters not being perfectly centered under 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:
Time to traverse 28 cm/right to left: 2.324219; 2.699219; 2.589844; average: 2.5377601
Time to traverse 28 cm/left to right: 2.167969; 2.16796; 2.224219; average: 2.186716
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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:
Taking the two averages and adding them together and dividing by two I have 2.3622383. I was faster in hitting the timer for the left to right measurements so that would skew my accuracy. Additionally the marble did not travel in a perfectly straight line and did not follow the same angle every time, so the marbles all traveled different distances.
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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 marble was not moving at the beginning of the timed interval. 2.3622383 was the average speed to traverse 28 cm. I think the marble would be traveling faster than the average the further it got from the beginning point.
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You don't appear to have calculated an 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:
Initial speed, average speed, and a tie for change in speed and final speed. The initial speed would be zero. The average speed would include the final speed with the slower speeds to bring it to a lower number. The change between the initial speed and the final speed would be the same as the final 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 marked 27 cm as the final point for the marble to reach. I also made marks at 9cm and 18cm, dividing the ramp evenly into 3 parts. I timed the time it took the marble to reach this points and repeated the experiment 3 times. The raw times it took to get to the first point were: .8554688; .703125; .7210938
The second point: .453125; .4804688; .484375
The third point: .375; .375; .3125
Average time to travel first 9 cm: 0.75989586666
Avg time to travel second 9 cm: 0.47265626666
Avg time to travel the third 9cm: 0.35416666666
The time it took the marble to travel 9cm decreased as the marble travel further from the initial point, thus supporting my theory of the marble traveling faster as time increased.
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&#Good responses. See my notes and let me know if you have questions. &#