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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.
#$&* Your general comment **
6/26/11 1:39 am
#$&* Will a steeper ramp give greater or lesser time? **
Timing a Ball down a Ramp
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 interval will be the least for the steepest ramp.
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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):
The time interval would be decresing as the slope increased. The
greater the slope the faster the ball will roll beacause there is
greater potential energy which turns in to a greater kenetic
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.
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):
1.813
1.734
1.813
1.791
1.828
1.781
1.719
1.75
1.797
1.734
These are the time intervals for the ball rolling from right to
left 5 times and then from left to right 5 times where the ramp
was laying on one domino.I was thinking that this can relate to
acceleration and potential/kenetic energy.
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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):
1.188
1.203
1.172
1.188
1.156
1.188
1.234
1.172
1.156
1.141
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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):
0.969
0.875
0.844
0.843
0.844
0.984
0.984
0.969
0.922
0.986
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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):
0.938
0.923
0.953
0.953
0.923
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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):
0.891
0.875
0.953
0.875
0.923
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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):
These results support my hypotheses.The steeper the slope the
less time it took for the ball to reach the end of 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.
Your answer (start in the next line):
The average Velocity will be increase as the slope increases.
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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 final velocity is increasing with each increse in slope. This
is why the average velocity increases as well.
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How might you verify whether your speculations are indeed valid
explanations?
Your answer (start in the next line):
You could take the average time it took the ball to travel the
same distance for each slope. Then with this information you
could find the average velocity's for each slope and you would
see that they do indeed increase for each increase in slope.
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Do your data conclusively show that the disk made a difference?
Your answer (start in the next line):
Yes albeit a slight difference. You can see that it took slightly
more time for the ball to travel the distance.
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Do your data conclusively show that the piece of paper made a
difference?
Your answer (start in the next line):
No. The paper made very little difference if any.
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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):
Very thin. I would say up to a 1/16 of an inch.
The paper had little effect but the cd did have an effect. So I
chose a measurement that would be between those two thicknesses.
The best way would be to have a mechanism that when the ball was
released it started the timer automatically and when the ball
struck the bracket the timer was automatically stopped.
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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):
The difference would have been greater because the slope would
have decreased.I think that at a less steep slope the change that
the paper would have would be more evident. The ball would be
moving more slowly down the ramp which would allow you see the
difference more accurately.
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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 change in velocity is much quicker in the 3 domino setup.
This would be evident by the change in velocity vs. the time
interval for the two slopes.
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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 hr
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*#&!
&#Very good data and responses. Let me know if you have questions. &#