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Phy 121
Your 'ball down ramp' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
#$&* Your general comment **
#$&* Will a steeper ramp give greater or lesser time? **
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A ball is timed as it rolls from rest to the end of a ramp. The slope of the ramp is varied. Preliminary conclusions are drawn about the motion and the effect of ramp slope. A subsequent lab exercise uses the data from this lab to reach additional conclusions.
Most students report completion times between 45 minutes and 75 minutes hour, with a few reporting times as short as 25 minutes or as long as 2 hours. Median time of completion is around 1 hour.
Timing Ball down Ramp
The picture below shows a ball near the end of a grooved steel track (this steel track is a piece of 'shelf standard'); the shelf standard is supported by a stack of two dominoes. Your lab materials package contains two pieces of shelf standard; the shelf standard shown in the figure is white, but the one in your kit might be colored black, gold, silver or any of a variety of other colors.
If a ball rolls from an initial state of rest down three ramps with different slopes, the same distance along the ramp each time, do you think the time required to roll the length of the ramp will be greatest or least for the steepest ramp, or will the interval on the steepest ramp be neither the greatest nor the least? Explain why you think you have correctly predicted the behavior of the system.
Your answer (start in the next line):
I would think that the steepest ramp would have the smallest time interval. As the slope, or steepness, increased it would make sense to me that the ball would take less time to travel the same distance. If we think of the system as a graph, the steeper the slope is the greater the acceleration and thus the less time it will take to travel the same distance.
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If we write down the slopes from least to greatest, next to the time intervals observed for those slopes, would you expect the time intervals to be increasing or decreasing, or do you think there would be no clear pattern? Explain why you think you have correctly described the behavior of the numbers in the table.
Your answer (start in the next line):
I believe that there would be a clear pattern between the slope and time interval. I would expect that as each slope increased the time interval would decrease. I feel that I am correct about this because based on what I’ve learned in this class, it makes sense.
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Set up the shelf standard ramp on a reasonably level table, using a piece of 30-cm shelf standard and a single domino under the high end of the ramp. Position the dominoes so that the last .5 cm of the ramp extends beyond the point where the ramp contacts the domino,.and do the same in all subsequent setups.
Set the bracket on the table, touching the lower end of the ramp so that a ball rolling down the ramp will strike the bracket..
Mark a point about 3 cm below the top end of the ramp. Place a domino on the ramp to its high end is at this point, and place the ball just above the domino, so the domino is holding it back. Quickly pull the domino away from the ball so the ball begins to roll freely down the ramp. Allow the ball to roll until it strikes the bracket.
The bracket will probably move a little bit. Reset it at the end of the ramp.
Determine how far the ball rolled from release until it struck the bracket.
Now repeat, but this time use the TIMER. The first click will occur at the instant you release the ball, the second at the instant the ball strikes the bracket. Practice until you are as sure as you can be that you are clicking and pulling back the domino at the same instant, and that your second click is simultaneous with the ball striking the bracket.
When you are ready, do 5 trials 'for real' and record your time intervals.
Then reverse the system--without otherwise changing the position of the ramp, place the domino under the left end and position the bracket at the right end.
Time 5 trials with the ramp in this position.
In the space below, give the time interval for each trial, rounded to the nearest .001 second. Give 1 trial on each line, so that you will have a total of 10 lines, the first 5 lines for the first system, then 5 lines for the second system.
Beginning in 11th line give a short narrative description of what your data means and how it was collected.
Also describe what you were thinking, relevant to physics and the experiment, during the process of setting up the system and performing the trials.
Your answer (start in the next line):
1.500
1.609
1.766
1.633
1.406
1.563
1.422
1.414
1.398
1.422
The above data represents 5 time trails in each direction (right to left, left to right) for a ball from release to hitting the bracket. The timer was clicked at release and then again when the ball traveled down the ramp and made contact with the bracket. The experiment was setup as directed in the instructions. Relating to physics, I was careful to make my setup correct to the directions in order to be as accurate as possible. I am interested to see how the time interval will change as the ramp slope increases.
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Now place two dominoes under the right end and repeat the process, obtaining the time interval for each of 5 trials.
Then place the two dominoes under the left end and repeat once more.
Enter your 10 time intervals using the same format as before.
Your answer (start in the next line):
1.219
1.242
.891
1.125
1.141
1.055
.922
1.016
.939
1.000
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Repeat the preceding using 3 dominoes instead of 2. Enter your 10 time intervals using the same format as before.
Your answer (start in the next line):
.891
.820
.828
.734
.633
.797
.656
.797
.641
.703
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Repeat the preceding again, still using the 3 domino setup, but this time place a CD or a DVD disk (or something of roughly similar thickness) on the 'low' end of the ramp. You need time only 5 intervals, but if you prefer you may use 10. Enter your 5 (or 10) time intervals using the same format as before.
Your answer (start in the next line):
1.016
.938
1.016
.984
.938
.875
.914
.891
.922
.938
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Repeat the preceding one last time, still using the 3 domino setup, but remove the disk and replace it with a piece of paper. You need time only 5 intervals, but if you prefer you may use 10. Enter your 5 (or 10) time intervals using the same format as before.
Your answer (start in the next line):
.844
.750
.828
.914
.789
.953
.750
.875
.797
.906
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Do your results support or fail to support the hypotheses you stated in the first two questions, regarding the relationship between time intervals and slopes? Explain.
Your answer (start in the next line):
I believe that the data supports my original hypotheses that the time interval will go down as the slope increased. It is evident from the data that the increase in slope makes the ball go faster and the time interval to decrease.
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How do you think the average velocity of the ball is related to the slope of the ramp? Explain in as much detail as possible.
Your answer (start in the next line):
If we think of the ramp setup as a graph with the initial velocity of 0 m/s then the final velocity would increase with the increase in slope. As the ramp gets higher the final velocity gets higher. With this being said, with all the same initial velocity but a higher final velocity, the average velocity would also have to increase. So the average velocity of the ball is definitely related to the slope of the ramp. The steeper the slope the great the average velocity.
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Speculate on what it is that causes the average velocity on these ramps to change with slope.
Your answer (start in the next line):
As I stated above the final velocity is increased and this in turn makes the average velocity greater. When evaluating this data it would also make sense that the acceleration of the object was also increasing as the slope increased.
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How might you verify whether your speculations are indeed valid explanations?
Your answer (start in the next line):
I could use the data that I collected in conjunction with the known length of the ramp and determine not only the final velocity but also the acceleration of the ball.
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Do your data conclusively show that the disk made a difference?
Your answer (start in the next line):
I believe that my data does a pretty good job of showing that the disk did make a difference. It is evident that the time interval took longer on average when the disk was in place as oppose to when it was not.
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Do your data conclusively show that the piece of paper made a difference?
Your answer (start in the next line):
The data that I have for when the paper was in place does not conclusively show that the paper made a difference. This makes sense because the paper was relatively thin compared to the disk.
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Imagine that someone is placing different objects below the 'low' end of the ramp, and you are timing the ball. Assume that somehow the object placed below the 'low' end is hidden from you in a way that does not interfere with the timing process. Compared to the thickness of the DVD, how thin would the object have to be before you would be unable, using the TIMER, to observe a difference in times down the ramp?
Answer this question in the first line below. Express your answer in multiples or fractions of the thickness of a disk.
Starting in the second line, explain how you came to your conclusion, based on the results you obtained in this experiment. Also discuss how you could modify or refine the experiment, still using the TIMER, to distinguish the effect of the thinnest possible object placed under the 'low end.
Your answer (start in the next line):
I would feel like that if the thickness of an object got to that of 1/4th the thickness of a DVD, I probably would not be able to tell the difference with the timer program.
I come to this conclusion because it looks like a piece of paper is about a fourth of the thickness of a DVD and I couldn’t tell the difference when the paper was in place. I could use the timer program and place objects of different thickness underneath the low end of the ramp and take time intervals until I could no longer detect a difference.
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Had you placed the disk below the 'low' end of the ramp in a 1-domino setup, do you think the difference in times would have been greater or less? Do you think you would be better able distinguish the presence of a thinner object using the 1-domino setup, or the 3-domino setup? Explain your reasoning below:
Your answer (start in the next line):
If I had placed a disk under the low end of the ramp in the 1-domino setup, I believe that the difference in time would have been greater. I believe that you would better be able to distinguish the presence of a thinner object using the 1-domino setup as oppose to the 3-domino setup. It just makes sense because a thinner object would have a greater effect on the slope of a smaller slope.
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Does the ball's velocity change more or less quickly with the 3-domino setup or the 1-domino setup? Explain as best you can how you could use your results to support your answer.
Your answer (start in the next line):
The ball’s velocity changes more quickly with the 3-domino setup as oppose to the 1-domino setup. I could use my data to determine the average acceleration of the ball for each change in slope. Acceleration is the rate at which velocity changes in relation to the distance covered.
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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?
Your answer (start in the next line):
1.75 hours
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*#&!*#&!
&#Your work on this lab exercise looks very good. Let me know if you have any questions. &#