Lab 2
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School
College of DuPage *
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Course
2111
Subject
Mathematics
Date
Feb 20, 2024
Type
Pages
4
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Lab 02
Freefall Acceleration
In this lab we will calculate the freefall acceleration of an object by fitting equations to both its position
and velocity graphs. We will use the methods we learned in Lab 01. The instructions will not be as
detailed as in Lab 01, so you may want to review those instructions or have them handy.
Note:
Because we want to be as precise as possible with our
measurements in this lab, we’re going to make a correction
we didn’t make in Lab 01.
The software actually measures the distance the object falls
by measuring the change in angle the object makes with the
horizontal.
Since the object is falling slightly in front of the
wall, the object will have only fallen 0.95 meter (95cm) when
it appears that is has fallen 1.00 meter when comparing the
marks on the wall. (See diagram to the right)
Activity 1 – Video Analysis
1)
Download the input video file from the Lab 02 folder our Blackboard. It is available in both .mov
and .zip format.
2)
Repeat your analysis from Lab 01.
a.
Advance the video one frame at a time by pressing on the
frame-advance button on the bottom right portion of the screen until
the person’s hand is no longer touching the mass.
b.
Note the red frame number in the lower left corner where you stopped.
Click on the “Clip Setting” icon just to the left of the Scale Tool and type
this number in as the “Starting Frame”.
c.
Create a coordinate system with the origin very near the mass.
d.
Calibrate the distances in the clip by saying that the distance between
the two long vertical lines on the white background is 0.95m (95cm)
3)
Once you’re set, create a new point mass and mark off the position of the
mass as it falls, frame by frame, using your cursor and the shift key.
4)
Now export your data as a coma delimited “.csv” file.
Activity 2 – Motion Analysis and Graphing
Note:
These instructions are assuming you are using the free version of Excel available to COD student.
If for some reason you decide to use another spreadsheet software (e.g. Googlesheets), the instructions
will be similar, although debugging may be difficult.
1)
Select the file you saved in Activity 1. You will see your data set with the time recorded in column
A, the x position recorded in column B and the y position in column C. (Note that since the video
is taken sideways, the x axis represents the vertical distance.)
2)
Find the average velocity (Dx/Dt) in column D just as we
did in Lab 01. (i.e. in D4 type
=(B4-B3)*30
).
3)
Find the average acceleration (Dv/Dt) in column E, similar
to what we just did for the velocity.
4)
Create graphs of position vs time and velocity vs time.
(Remember that you need to have the same number of
cells in both the vertical and horizontal data sets. So, if your velocity
begins in cell D4, your time should begin in A4.)
5)
Find a trendline for both these graphs and display the equations. Note that the trendline for the
positive vs time graph is
NOT
linear. You will need to change to the appropriate equation by
using the “Format Trendline” option.
6)
Find the average value of the accelerations calculated in Column E.
7)
Instructor Check:
Write your name in large letters on the spread sheet above the two plots you
just created.
Log into the lab’s zoom meeting and share your screen so the instructor can see
your plot, name, and trendline equation.
Wait for the instructor to tell you to continue.
Activity 3 – Discussion
1)
What was the average value for the acceleration you found in Step 6 of Activity 2?
9.27E+00
2)
The equation for the trendline on the position vs time graph contains three numerical values.
What is the physical meaning of each of those values?
The co-efficient of the x^2 term is the acceleration.
The co-efficient of the x term is the velocity
And the last term is the position.
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