course Phy 201
5/3 1430
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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:
For the ramp I used our physics book: Physics by Giancoli: Fifth Edition.(ISBN 0-13-611971-9). This book measures 26.2cm long. I used a ruler that was 1cm thick to prop up my book. For my ball I used the 2.5cm diameter steel bearing that was supplied in our lab kit package This ball definitely speed up as it traveled down the book . The ball would start rolling toward the opening of the book and then would straighten up after it had traveled about a quarter of the book. The ball traveled approximately 28cm as it travelled from one end to the other. I calculated this by using a string to gauge how far the ball rolled. I then measured the string.
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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 first measured the time as the ball travelled from my right to left. I would start the timer when I would release the ball and stop the timer when the ball would drop off of the book. I obtained the following 5 measurements:
2.011719
1.871094
1.820313
1.769531
1.878906
My measurements from left to right are as follows:
2.550781
2.519531
2.570313
2.5
2.46875
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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:
Moving from Right to Left the ball averaged 1.87 seconds to travel down the incline. So its average speed is 14.97cm/sec.
Moving from Left to right the ball averaged 2.52 seconds to travel down the incline. So its average speed is 11.07cm/sec.
I believe my measurements are accurate within .5cm/sec. I state this because since I am starting and stopping the clock there is no way that I can precisely start and stop the timer at the exact moment that I start and stop the ball.
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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 measured the halfway point on my book and taped a line across at that point. I then started the timer when the ball started rolling, again when it crossed the halfway line, and finally when the ball fell off of the book. I then compared the two time measurements. If the first measurement was longer than the second then I knew that the ball was speeding up. Below are my measurements:
1st half 2nd half
1.4453 .4453
1.3828 .5703
1.375 .5781
1.1484 .5468
1.5 .5390
As we can see from the measurements, it takes almost 3 times as long to travel the first half of the book as it does the second half. So our ball is definitely speeding up.
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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?
45 minutes.
&#Very good responses. Let me know if you have questions. &#