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PHY 201
Your 'initial timing experiment' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** Initial Timing Experiment_labelMessages **
I retried this experiment with the car from the materials package which I did not have when I tried this course last semester.
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Note: The majority of student report taking less than an hour on this experiment, though a few
report significantly longer times.
Take reasonable care to get good data in this experiment. Try to do the timing as accurately
as possible. Measurements of length, height, etc. should be reasonably accurate (e.g., with a
meter stick or ruler you can measure to withing +- 1 millimeter, but it's not necessary to try to
determine fractions of a millimeter).
In this experiment you will use the TIMER program, a hardcover book, the toy car that came in
your lab materials package (or, if you do not yet have the package, a cylinder or some other
object that will roll along the book in a relatively straight line), and a ruler or the equivalent (if
you don't have one, note the Rulers link, which is also given on the Assignments page).
The book's cover should be straight and unbent.
The toy car (or other object) should roll fairly smoothly.
Place the book on a flat level tabletop. You will prop one end of the book up a little bit, so
that when it is released the object will roll without your assistance, gradually speeding up, from
the propped-up end to the lower end. However don't prop the end up too much. It should
take at least two seconds for the ball to roll down the length of the book when it is released
from rest. For a typical book, a stack of two or three quarters placed under one end works
well.
Using the TIMER program determine how long it takes the ball to roll from one end of the ramp
to the other, when released from rest. Once you've got the book set up, it takes only a few
seconds to do a timing, so it won't take you long to time the object's motion at least three times.
Determine how far the object travels as it rolls from its initial position (where you first click the
timer) to its final position (where you click at the end of the interval). This will probably be a bit
less than the length of the book, due to the length of the object itself.
Determine how much higher one end of the book was than the other, and how far it is from the
supports (e.g., the stack of quarters, or whatever you used to support one end) to the end of the
book which rests on the table.
Then reverse the direction of the book on the tabletop, rotating the book an its supports (e.g.,
the stack of quarters) 180 degrees so that the ball will roll in exactly the opposite direction.
Repeat your measurements.
In the box below describe your setup, being as specific as possible about the book used (title,
ISBN) and the object being used (e.g., a can of vegetables (full or empty; should be specified)
or a jar (again full or empty); anything round and smooth that will upon release roll fairly slowly
down the incline), and what you used to prop the object up (be as specific as possible). Also
describe how well the object rolled--did it roll smoothly, did it speed up and slow down, did it
roll in a straight line or did its direction change somewhat?
your brief discussion/description/explanation:
I constructed my ramp out of my 6th edition 'Physics' textbook by Giancoli, ISBN: 0-13-
060620-0 on my dining room table, a relatively level and flat surface. The length of the ramp
was 215mm. At the starting place of rest, the ramp measured 50mm high off the table
surface, and 40mm at the finish place, an overall difference of 10mm. To establish the height
of the ramp, I used a AA Energizer battery, which when measured aproximately 14.25mm.
I used the green Hot Wheels car from my materials package which is a model of a 2008
Mitsubishi Lacer Evolution. The car was about 76mm long when I measured it.
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mark)
In the space indicated below report your data. State exactly what was measured, how it was
measured, how accurately you believe it was measured and of course what the measurements
were. Try to organize your report so the reader can easily scan your data and identify any
patterns or trends.
your brief discussion/description/explanation:
I timed the object using a pen as a starting gate at 0mm on the ruler and had the ruler stop at
the edge of the book at 215mm. I set my metric ruler lengthwise down the ramp, so I could
align the starting gate and also sight the finish so I could stop the timer at the same moment for
each consecutive attempt. I believe my experiment was conducted in a manner that would give
the least variables possible with each attempt. Without a mechanized starting gate and weight
sensing finish timer, it is impossible to get an exact reading each time, though I believe given
human error the readings below were accurately found.
My Timer results for the first direction were as follows:
1 372.9102 372.9102
2 374.0684 1.158203
1 451.792 451.792
2 452.9482 1.15625
1 518.0928 518.0928
2 519.3125 1.219727
For the opposite direction the results were:
1 629.3672 629.3672
2 630.7939 1.426758
1 696.584 696.584
2 698.0713 1.487305
1 762.0371 762.0371
2 763.7119 1.674805
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Using your data determine how fast the object was moving, on the average, as it rolled down
the incline. Estimate how accurately you believe you were able to determine the object's
average speed, and give the best reasons you can for your estimate of the accuracy.
your brief discussion/description/explanation:
For the first direction (right to left) the car traveled at the following rates:
21.5cm/1.158sec = 18.57cm/sec
21.5cm/1.156sec = 18.6cm/sec
21.5cm/1.2198sec = 17.63cm/sec
The vAve for all three right to left readings was 18.27 cm/sec.
For the opposite direction (left to right) the car traveled at the following rates:
21.5cm/1.427sec = 15.07cm/sec
21.5cm/1.487sec = 14.46cm/sec
21.5cm/1.675sec = 12.84cm/sec
The vAve for all three left to right readings was 14.12cm/sec.
The difference between the average speeds of the car was 4.15cm/sec which suggests that my
table was not as level as I thought. The discrepancy in the individual readings from one result to
the next suggests that my release of the starting gate the accuracy of my timing vs. the reading
of the distance on the book are also potential causes for inaccuracy.
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How fast was the object moving at the beginning of the timed interval?
According to your previous calculation, what was its average speed during this interval?
Do you think the object, when it reached the lower end of the book, was moving at a speed
greater or less than the average speed you calculated?
your brief discussion/description/explanation:
The object was at rest at the beginning of the timed interval, so the vAve was 0m/sec. I know
this because the first reading for each timing the time split of the first reading was the same as
the first reading. The speed was greater at the lower end of the book than at the higher end.
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List the following in order, from least to greatest. Indicate 'ties': The object's initial speed, its
final speed, its average speed, and the change in its speed as it rolled from one end of the
book to the other.
your brief discussion/description/explanation:
The car's intitial speed, the car's changed speed as it rolled from one end to the other which
results in the average speed, and it's final speed which is the greatest.
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Devise and conduct an experiment to determine whether or not the object is speeding up as it
rolls down the incline. If you have set the experiment up as indicated, it should seem pretty
obvious that the object is in fact speeding up. But figure out a way to use actual measurements
to support your belief.
Explain how you designed and conducted your experiment, give your data and explain how
your data support your conclusions.
your brief discussion/description/explanation:
My new experiment was conducted with the same ramp as before: the Physics textbook, a AA
battery, the 21.5cm length, and the car as before. For this experiment I added a marker at
the 10.75cm, halfway point, and clicked the timer at this point as well.
By collecting three readings instead of only two, I am able to show the increase in velocity, as
the object is rolling slower for the first half of the ramp than the second half.
My results were:
1 4554.663 4554.663
2 4555.513 .8496094
3 4555.868 .3554688
I can see just by observing the timer results that the time the object took to travel the first
10.75cm is more than the time is took to travel the final 10.75cm, .8496094sec. as opposed to
0.3554688sec for the final leg.
I calculated a vAve for the first 10.75cm as 12.62cm/sec (10.75/.8496=12.62). The vAve
for the final 10.75cm/.3555sec = 30.24cm/sec. The total vAve was 21.5cm/1.205sec =
17.84cm/sec.
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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?
1 hour
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You may also include optional comments and/or questions.
For review, I retried this lab with the car as I did not have the car when I first tried PHY 1 last semester.
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&#Very good data and responses. Let me know if you have questions. &#