initial timing experiment

Phy 121

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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Initial Timing Experiment

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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).

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.

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 solid glass marble, a small can of tomato paste (full or empty?), a ball-point pen), 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?

Note:  Don't trust this form.  Compose your answer in Notepad or a word processor, saving it every few minutes, then copy and paste it into the box.  Power could surge, your computer could malfunction, in any of a number of ways the work you put into this form could be lost.  Compose it elsewhere and keep a copy.

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The book I used was the 6th edition Physics book by Giancoli. For this experiment, I used a 10.5 ounce can of soup. My ramp was proped up by two pamphlets that added together equaled about ~1.2cm thick. I had my ramp set up on the floor of my house (wooden) next to my computer. The can started very slow, but in the ~28and1/4cm of the book, it reached a fairly quick speed. The can did roll in a straight,smooth line from one end of the book to the other.

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In the box 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 see any patterns that might occur.

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To start, I measured the width of the objects I was using to prop up the book, finding they measured rougly 1.2cm thick (accurate within 2cm, but the pamphlets I used were not staying perfectly closed). I then placed the book on the pamphlets and measured the far end at 3.6cm from the ground and the start of the ramp at 5cm from the ground. The difference between the ends being 1.4cm and the height of the pamphlets I used to prop the book being 1.2cm, I must have 2cm of error in my measuring. From here, I measured the length of the book to be 22and1/4cm, probably accurate within 1cm. To begin my experiment, I held the can as close as possible to the high end of the ramp with one hand and had my other on the mouse ready to begin timing using the TIMER program. I did the experiment this way in hopes of minimizing the difference between starting TIMER and the can actually rolling. I stopped the timer when I saw the can fall off the book. On my first three trials respectively, I measured times of 2.36 seconds, 2.36 seconds, and 2.48 seconds all rounded from the thousanths place. Next, I reversed the direction of the ramp and got times respectively of 3.34 seconds, 3.14 seconds, and 3.15 seconds. My best guess for the discrepency in the times on the two different directions of the ramp would be slightly uneven floors, and the pamphlets I used to prop the book being in slightly different positions.

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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.

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My average time over my first three trials was and even 2.4 seconds. This would mean the can was traveling at an average of 12cm/second. My results can be no more accurate than to two significant figures since my average time only has two significant figures. For the trials with the ramp facing the opposite direction, my average time was 3.21 seconds. This would mean that on these trials the can was traveling at approximently 8.80 cm/second. This is accurate to the hundredths place since all my calculations are to the hundredths place.

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Devise and concuct 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.

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To test if the can was speeding up, I did the exact same experiment as above, but in two steps. First, I will measure the can traveling half the distance (~14cm). Then, I will measure the can traveling the full distance (~28cm). If the first time measurment is half the total time measurment, then there is no acceleration. If the first is more than half the total, it is decelerating. Finally, if the first is less than half the total, the can is accelerating. Upon doing the experiment, I had a slightly flatter ramp than my first trials with a height difference from end to end of .8cm. My frist two tests, I had the can going exactally 1/2 the length of the book and got two respective times of 3.12 sec. and 3.09 sec with an average of 3.15 seconds to travel half the length of the book. Then, I ran the same tests except with the can rolling the entire length and got two respective times of 3.42 and 3.5 seconds with an average of 3.46 seconds. This shows that the can traveled the first 14cm in roughly 3.09 seconds and the last 14cm in roughly .41 seconds. From what I can tell by watching the test take place, these numbers seem very close to the actual times and definately accurate eneough to represent that about half way down the ramp the can gains substantial speed.

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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: 

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45minutes including the time to gather materials.

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You may add optional comments and/or questions in the box below.

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&#Your work looks good. Let me know if you have any questions. &#