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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.
** Initial Timing Experiment_labelMessages **
2/7/13 11:18am
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Copy this document, from this point to the end, into a word processor or text editor.
• Follow the instructions, fill in your data and the results of your analysis in the given format.
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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:
The book I used is called Lifetime Health by Holt, ISBN: 0-03-067201-5. The length of the book is about 282mm and the depth or height of the book is about 26mm. I rolled a pink Crayola Magic Marker down the ramp. The marker with the lid is about 137mm long and the diameter is about 13mm. To prop up the book I used a domino that came with the initial lab materials. It has 6 yellow dots and 4 brown dots. The height of the domino that propped the book up is about 7mm.
The marker rolled smoothly down the ramp and its speed gradually increased as it rolled. It did roll slight towards the end of the marker with the lid. I tried it without the lid and it did the same, so I left the lid on when I timed it.
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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:
I measured the time it took the marker to roll from one edge of the book to the other using the TIMER program provided. The times appear to be accurate within .05s.
When I rolled the marker from right to left the times were
1.968
2.017
1.871
1.84
1.913
When I turned the book 180 degrees and rolled the marker from left to right the times were
2.072
2.0
2.064
1.911
2.009
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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:
I took the length of the ramp, 282 mm, and estimated that the marker rolled 280 mm during the timing interval. So I multiplied 280*5=1400mm and added together the times from the five trials to get 9.609 right to left and 10.056 left to right. I divided 1400 by both number to get the average speeds of 145.7mm/s R-L and 139.2mm/s L-R. The timing should be accurate minus the possibility of human error. I could have clicked the mouse a little too soon or a little late.
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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:
It wasn’t in the instructions to time during the first interval so I’m not sure how to calculate how fast the marker was moving during the first interval without doing the experiment again and timing the interval. I can estimate that the marker was moving slower at the beginning of the interval and faster at the end. Therefore the marker was moving slower in the beginning of the interval than the average speed I calculated. I would estimate that the marker was moving about 100mm/s during the first interval.
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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:
I don’t understand what you mean by Indicate ‘ties’.
From least to greatest: initial speed, average speed, change in speed, 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:
The experiment was set up just like the previous one, except I put a small piece of black electrical tape on the ramp at 141mm to signify the middle of the ramp. When I timed the marker this time I used two intervals, the time it took from the top of the ramp to the middle and from the middle to the end of the ramp. I only timed the marker rolling from left to right. My results were
1st half 2nd half
1.64 .0649
1.592 .704
1.616 .673
1.536 .712
1.952 .672
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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?
Including the time to gather the materials it took me about an hour and ten minutes to complete the experiment and the write up.
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You may also include optional comments and/or questions.
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*#&!
&#Your work on this lab exercise is good. Let me know if you have questions. &#