PASCO Xplorer GLX, User Manual

Page: 125 / 152

X p l o r e r G L X U s e r s ’ G u i d e 119
5. Create a calculation for ln(r/r
0
)
a) Press to return to the Home Screen; press to open the Calcu-
lator.
b) On a blank line, enter:
ln(r/r0)
c) To insert the ln() function, press to open the Functions menu, use
the arrow keys to highlight ln(), and press .
d) The Calculator will prompt you on the next line to enter the value of r
0
.
Type the initial relative temperature and press .
6. Make a graph of ln(r/r
0
) versus t.
a) Press to return to the Home Screen; press to open the Graph
display.
b) Press to open the Graphs menu; press to select New Graph
Page.
c) Press twice to highlight the data source menu. From the menu
select ln(r/r0).
7. Apply a linear fit and find the value of k.
a) Press to open the Tools menu; press to select Linear Fit.
b) Press the down arrow key to make the dashed box surround the entire
data set.
c) The slope of the best-fit line equals k.
k = _________________ (include units)
Now that you have experimental values for the constants r
0
and k, you can substi-
tute them into Equation 2 and compare that model to the collected data.
8. Enter Equation 2 into the Calculator using your experimental values of
r
0
and k.
a) Press to return to the Home Screen; press to open the Calcu-
lator.
b) On a blank line, enter:
r model = r0 * e^(-k*t)
Enter this calculation
Calculator will prompt
you for value
F3
F1
F1
F1
F4 7
?!
Press to make the dashed
box surround the entire data set
F3 5
jkl
Enter this calculation
Enter experimental value for k
Do not enter a value for t
F3