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PHY 231
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 30 minutes and 1 hour, with a few reporting times as short as 15 minutes or as long as 2 hours. Median time of completion is around 45 minutes.
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.
I believe that the time required for the steepest downhill ramp will be the least because the more you increase the steepness of the ramp, the greater you increase the ball's acceleration down the ramp. In addition, the higher the initial height of the ball, the greater gravitational potential present and that is converted into kinetic energy, the motion of the ball. If the ball starts at rest at the top of each ramp, the ramp with the greatest initial height, the most steep, will give the ball the most potential energy that converts into kinetic energy, giving the ball the greatest velocity.
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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.
I would think that the time intervals would be decreasing from least to greatest, as a result of the steepness of the slopes which increase the ball's acceleration and potential energy converted into kinetic energy. The steeper the slope, the higher initial starting height. Thus, steeper slopes increase not only the acceleration, but also the amount of potential energy just based on position, and consequently the amount converted into kinetic energy.
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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. 23.6 cm
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.
Trial ( Original Position )
1 1.402 s
2 1.391 s
3 1.395 s
4 1.379 s
5 1.395 s
Trial ( Reverse Position )
1 1.379 s
2 1.413 s
3 1.376 s
4 1.385 s
5 1.400 s
The first set of data displays the five trials I recorded with the ramp in its original position, facing me. The second set of data displays five trials with the ramp in the reversed position. I collected it by setting up the system in-between runs as followed: I placed the entire system on a flat computer desk, a foot lower than my height sitting down. I measured and marked a spot on my desk for my domino to go underneath the ramp. Then, I placed my domino in that spot every time to ensure consistency. I centered the ramp on the domino for better results. Then, I measured a place 3 cm from the edge of the ramp for the ball to rest, held in place by the domino. I marked the center of the end of the ramp in pencil as well, for the place to line up the bracket. I lined up the edge of the ramp and bracket with the edge of the computer desk each time as well for best results. I ran through 20 practice trials before recording for accuracy and accountability. My results were very close and precise too. I wanted to make the set-up conditions were as consistent as possible. I was very careful and cautious for optimum performance.
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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.
Trial ( Original Position )
1 1.012 s
2 1.031 s
3 1.035 s
4 1.035 s
5 1.047 s
Trial ( Reverse Position )
1 1.023 s
2 1.042 s
3 1.043 s
4 1.019 s
5 1.033 s
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Repeat the preceding using 3 dominoes instead of 2. Enter your 10 time intervals using the same format as before.
Trial ( Original Position )
1 .672 s
2 .680 s
3 .688 s
4 .695 s
5 .673 s
Trial ( Reverse Position )
1 .695 s
2 .665 s
3 .678 s
4 .684 s
5 .641 s
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Do your results support fail to support the hypotheses you stated in the first two questions, regarding the relationship between time intervals and slopes? Explain.
Yes, the results support my hypothesis wholeheartedly. The time intervals decreased with increasing slope. As the initial height increased with each added domino, the acceleration increased down the slope. I believe the added initial height contributed to the added kinetic energy that the ball experienced down the ramp.
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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.
The ball started at rest, 0 cm/s. The ball had the same length, about 26.5 cm, to travel down the slope at the same time. The ramp's position on flat desk stayed the same. Thus, the faster the ball accelerated, due to the increased initial height of the ramp each time, the higher the overall final velocity. Thus, the average velocity was half of the final velocity. The quicker the ball was able to go down the slope, the shorter the time interval. And consequently, the average velocity increased with increasing slope.
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Speculate on what it is that causes the average velocity on these ramps to change with slope.
I believe the gravitational potential energy associated with the initial height the ball starts from at the top of each ramp is solely responsible for the higher overall average velocity. A greater acceleration accompanies a higher initial height, from the increase in the number of dominoes supporting the ramp. The fast the ball is able to accelerate, the greater the final, and consequently the average velocity. I believe this holds true as long as gravitational pull ( and not air resistance, friction, etc. ) remains the dominating force in the object traveling down the ramp.
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How might you verify whether your speculations are indeed valid explanations?
I could verify my speculations by doing the same experiment with different materials of the ramp and the ball. I could test a ramp of greater and lesser length to verify that my observations hold true. In this experiment, you could measure two points where the ball is on the ramp for further analysis to calculate and compare average velocities on ramps with different slopes. Graphing and tracking the ball's position and velocity versus time would also help solidify my results.
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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?
50 Minutes
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&#Very good responses. Let me know if you have questions. &#