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, 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 on the Assignments page).
• The book's cover should be straight and unbent.
• The 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.
• 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. Time the object's motion at least three times.
• Determine how far the object actually travels as it rolls from one end to the other.
• Determine how much higher one end of the book was than the other, and how far it is from one end to the other.
Then reverse the direction of the book on the tabletop, rotating the book and its prop 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?
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your brief discussion/description/explanation:
In my setup I used the physics book (Physics by Giancoli Sixth Edition, ISBN: 0-13-060620). It is propped up on one end using a domino that is approximately one centimeter thick. The object used to roll was a full can of 16 oz soup. The can rolled smoothly and in a straight line and appeared to be speeding up.
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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 average speed of an object rolling down an incline was measured. The distance that the object rolled was 28.4 cm. The incline was at 1 cm. The measurements were taken by manually releasing the object from a stop and timing the distance using the TIMER program. The release point was attempted to be the same each time by marking the object. Even though steps were taken to acquire the most accurate results, some variation will occur from the actual start and stop points of the object. The observed measurements are given below:
Roll Time(sec) Average Speed (cm/sec)
1 2.1875 12.9829
2 2.21875 12.8000
3 2.234375 12.7105
When rotating the direction of the experiment the measurements are as follows:
Roll Time(sec) Average Speed (cm/sec)
1 2.015625 14.0899
2 2.132813 13.3157
3 2.101563 13.5138
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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:
The average speeds of each roll are given in the question above, but I will give an average speed of all three rolls.
One direction =12.8311 cm/sec
The other direction = 13.6298 cm/sec
I believe the accuracy is within 0.3. The reason for the accuracy is because actually starting the object in the same place, clicking the mouse button for the timer, and the actual stop position can vary from attempt to attempt.
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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 the book directly in the middle making two halves. I measured the time for each half using the TIMER program. The results are as follows:
Roll Time(sec) First Half Time(sec) Second Half
1 1.695313 0.7578125
2 1.664063 0.6953125
3 1.578125 0.7109375
The data clearly shows that it took less time to travel the second half of the distance. The average distance of the first half was 8.62785 cm/sec. The average speed during the second half was 19.6852 cm/sec.
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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?
1 hour
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You may also include optional comments and/or questions.
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&#This looks good. Let me know if you have any questions. &#