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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.
** #$&* Your general comment **
9/21 10am
** #$&* 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 believe the time required to roll down the steepest ramp will be the least. If there are
three ramps, slope should be increasing, greater slope acceleration will add much more
momemtum, shortening the interval required to complete the 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 would expect the time intervals to correspondingly increase with increase of slope.
Greater slope normally would include greater acceleration, less time, the opposite as
slope is diminished, time will increase.
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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):
1.904
1.838
1.832
1.967
1.992
1.648
1.680
1.641
1.581
1.682
The data collected is the time interval collected for each trial for the ball to move 27 cm
down the ramp. I marked my 4 cm spot from the top end of the ramp, placed the bracket
at the end of the ramp, and timed by release and sound as directed. The slopw would
have stayed the same, unless the surface was not completely level.
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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):
1.320
1.240
1.281
1.290
1.318
1.186
1.238
1.225
1.264
1.305
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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):
1.033
1.121
1.096
1.047
1.096
1.023
0.992
0.951
0.984
1.000
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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):
1.295
1.336
1.383
1.256
1.416
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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):
1.191
1.104
1.049
1.096
1.119
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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):
The results successfully support my earlier hypotheses that with the increase of slope,
the time interval decreased in consequence.
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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):
The average velocity is directly attributed to the slope of the ramp, because the degree
of the incline will ascertain the speed of the ball.
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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):
The degree of the curve is what causes the average velocity to change. The mass,
distance, are all constant for all trials. Greater incline perhaps creates less initial
pressure to hold ball back in place. Granted, air pressure resistance increases with the
velocity; however, there is less force keeping the ball stationary at greater slopes
providing more energy.
As we will see, stationary ball will remain stationary in the absence of forces.
It takes force to change the velocity of the ball.
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How might you verify whether your speculations are indeed valid explanations?
Your answer (start in the next line):
My speculations are valid, and the data supports this, because mass and distance
remain universal for all trials. The only being altered is the degree of slope, steepness,
and common sense tells me that a car with the same dimensions will increase in velocity
coasting down a steeper hill.
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Do your data conclusively show that the disk made a difference?
Your answer (start in the next line):
Yes, the disk expressed an slight increase in slope after timing trials ending on the
surface. The time interval slightly increased, and once the disc was removed, the time
interval resulted by decreasing due to greater slope.
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Do your data conclusively show that the piece of paper made a difference?
Your answer (start in the next line):
Yes, as stated above, the piece of paper was merely an element demonstrating the
change from the previous elevated slope via cd. The time interval increased with the
piece of paper, in comparison with the cd, as it should.
I suspect that the change in the time interval due to the slip of paper is much less than the uncertainties in your timing, and is hence undetectable with the human-triggered timer.
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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):
1/4
I took it down to a piece of plastic roughly 1/4 the size of the dvd, and still noticed slight
decrease in time interval; however, being that it was much more challenging to precisely
time, it seemed to be in correlation with simply the flat surface being the end marker
platform.
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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 would say that a one domino setup with the disk at the lower end would, compared to a
piece of paper in this setting, would yield a much longer time interval. It would be easier
to distinguish the presence of a thinner object using the three domino setup, because
there would be a greater difference in slope, which the recorded time interval differences
would be more acute.
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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):
Given that the one domino setup has a lower average velocity, I would conclude that the
three domino setup has high change in the ball's celocity. Taking the slope of each yeilds
a higher slope, greater rate of acceleration, for 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):
1.5 hours
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Good answers, but do see my notes.