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PHY 201
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.
** Ball Down Ramp_labelMessages **
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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):
The steepest slope should correspond with the shortest time interval. The ball should have greater acceleration on the steeper slope.
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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):
Decreasing. I believe that the steeper slope will allow the ball to accelerate more quickly down the ramp.
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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):
1.793
1.887
1.840
1.809
1.953
1.641
1.734
1.664
1.824
1.625
This is the ‘dt for a ball rolling down a ramp of length 27.1cm in length and elevated by one domino, .7cm high. Time is shown in seconds. The first five intervals are for the ball rolling right to left and the next five intervals, the ramp was spun 180 deg.
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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):
1.234
1.262
1.277
1.230
1.301
1.207
1.246
1.250
1.336
1.227
This is the ‘dt for a ball rolling down a ramp of length 27.1cm in length and elevated by two dominoes, 1.4cm high. Time is shown in seconds. The first five intervals are for the ball rolling right to left and the next five intervals, the ramp was spun 180 deg.
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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):
1.082
1.000
1.039
1.039
1.070
0.941
0.953
1.031
1.016
1.039
This is the ‘dt for a ball rolling down a ramp of length 27.1cm in length and elevated by three dominoes, 2.1cm high. Time is shown in seconds. The first five intervals are for the ball rolling right to left and the next five intervals, the ramp was spun 180 deg.
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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):
1.086
1.090
1.086
1.023
1.047
This is the ‘dt for a ball rolling down a ramp of length 27.1cm in length and elevated by three dominoes, 2.1cm high and a dvd beneath the lower end of the ramp. Time is shown in seconds.
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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):
1.047
1.055
0.930
1.001
This is the ‘dt for a ball rolling down a ramp of length 27.1cm in length and elevated by three dominoes, 2.1cm high and a piece of paper beneath the lower end of the ramp. Time is shown in seconds.
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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):
Yes, as the slope of the ramp increase, the time intervals got smaller.
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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 v_ave = ‘ds/’dt and ‘ds remained the same, then as ‘dt got smaller v_ave increased. Suppose 4/2 = 2 and 4/1 = 4. Four is obviously greater than two as the denominator decreased.
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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):
If v_ave increase, so does ‘dv. A_ave = ‘dv/’dt. As ‘dv increases, and ‘dt decrease, the result gets higher and higher. This means that the ball had greater acceleration on the steeper ramp than the less steep ramp.
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How might you verify whether your speculations are indeed valid explanations?
Your answer (start in the next line):
Use the data obtained and find the average ‘dt for each height ramp. Since we know ‘dt, you can find v_ave. With v_ave, you can find v_f and ’dv. This will allow you to find a_ave.
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Do your data conclusively show that the disk made a difference?
Your answer (start in the next line):
I would not say conclusively but it does appear that ‘dt was slightly higher when the dvd was placed. Average ‘dt with just the dominoes was 1.021 s and with the dvd beneath the lower end was 1.066 sec. This is close to within the error associated with the timer program and definitely within the human error. I do think that the dvd did cause v_ave to be smaller.
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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 average ‘dt with the paper was 1.002 seconds which would actually be faster than without. I don’t think you could say that the paper caused it to speed up so the data doesn’t show that it made a difference.
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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 feel that it might be possible to detect up to half the thickness of the dvd. The difference between no dvd and with dvd in average ‘dt was about 0.04, which is twice that of the error with the timer program (1/64 or 0.015 sec.) So half the thickness might be around 0.02 and fall within the error of the timer program.
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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):
I think it would be more noticeable because as a percentage, it would change the slope greater with one domino than with three domioes.
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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):
Since acceleration is greater, as answered above, the velocity changes more quickly with the three domino setup.
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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 hour
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&#Very good data and responses. Let me know if you have questions. &#