The computer setup of part III is to connect the photogate’s
stereo phone plug to Digital Channel on the interface. Open P06_FALL document in the
physics lab folder on the desktop. The graph in the document will display plots of
position and velocity versus time and a table of position, velocity, and acceleration versus
time. Next in order to setup the equipment turn the photogate head sideways so when you
drop the “picket fence” vertically from above you can have the “picket fence” move
through the photogate’s opening without hitting the photogate. After the partners decide
while trial is the best then they can compare data by drawing a box around the desired
area of your graph versus original graph and adding in a linear fit to see what the slope
(acceleration), speed, and velocity is of the object. To find the percent discrepancy we use
the formula*100%. Our percent discrepancy between the slope of the our velocity versus
time plot (9.73) and the accepted value of the acceleration of a free falling object (g=9.8)
was 0.70% while the percent discrepancy between the mean of the acceleration from the
table (9.7) and the accepted value of the acceleration of a free falling object (g=9.8) was
1.00%.
Unfamiliar Terms
:
•
Photogate
:
A device that measures the time between events that interrupt an infra
red beam. (http://en.wiktionary.org/wiki/photogate).
•
Percent discrepancy:
=*100% (from lab).
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Percent error
: =(from lab).
•
Motion sensor
: uses the pulses of ultrasound that reflect from an object to
determine the position of an object. (From lab).
•
Picket fence
: A clear plastic strip with uniformly spaced opaque bands (from lab).
•
Velocity
: The time rate of change of position of a body in a specific direction.
(dictionary.com)
•
Acceleration
: The time rate of change of velocity with respect to magnitude or
direction; the derivative of velocity with respect to time. (dictionary.com)
•
Speed
: rate of motion or progress. (dictionary.com)
•
Graph
: a mathematical picture of the motion of an object. (from lab)
Data:
Part I.
How close should you be to the motion
sensor at the beginning?
0.40m
How far away should you move?
0.70m
How long should your motion last?
4s
How fast should you move while you are
walking?
.175
Analysis:
Percent error
: =
•
Sample:
Percent discrepancy
: =*100%
•
Sample: 1.00%
Results and Conclusion:
This lab parts I and II was executed to teach students about the
relationships between the motion of an object (the student) and a graph of velocity and
time for the moving object while Part III of the lab was executed to teach students how to
measure the acceleration of an object in freefall. The end result for part I was that one of
us stood still from 02 seconds at .40m. Then moved backwards with constant velocity
for four seconds. Then stayed there for four seconds at 1.10 meters to finish off with a
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 Fall '11
 BrunoBauer
 Physics, Derivative, Acceleration, Velocity, Picket fence

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