Graphing Guidelines

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					                                                Physics Graphing Guidelines

When attempting to determine the “correct” relationship between two variables, several relationships should be tried to see
which provides the best fit. This is the one that should be chosen.

Refer to the document “GA & Logger-Pro Manual” to see instructions on how to plot and analyze your data.


Each Graph Should ALWAYS Include The Following:

1.       Each axis correctly labeled with what is being graphed on that axis (force, time, etc.) with the correct unit in its
         symbolic form (N, s, ...) in parenthesis after the unit.

2.       A title that includes:
         A.        On what the experiment was performed.
         B.        What was done?
         C.        Any variable(s) that was held constant
                   Examples:         “Ball Falling With Constant Gravity”
                                     “Car Rolling Down a Hill With Constant Mass”
                                     “Current in a Wire with Constant Voltage”

3.       A best fit line of curve “drawn” in.

4.       A caption, which includes the following items:
         A.      The type of relationship (linear, inverse, Inverse Square etc..).

         B.       Indicate how the two variables are related. As an example, if you have an inverse square relationship
                  between gravity and distance, you would state that: “The force of gravity varies in inversely with the
                  square of the distance.” In addition, give an example of what that statement means. Ex: If the distance
                  between the two objects doubled, the force between them would be one fourth as much.”

         C.       The equation. This will automatically appear when you have the line drawn in. Rewrite the equation in
                  your own hand replacing the x and y with the correct symbol of the variables being graphed. Include
                  any constants but exclude any “+/-“ values.

         D.       If the relationship is linear, indicate the value of the slope with the units. This will also automatically
                  appear when you have the line drawn in. The slope indicates a constant in the experiment and many
                  times can be determined from looking at the units of the slope. Indicate what the meaning of the slope is
                  if it can be determined. If it cannot be determined then state that it is “undetermined” or “has no
                  meaning”.


Graphs should NEVER include the following:

1.       Simply restate your axes as a title. Example: “Speed verse Time”

2.       Connect the dots as opposed to determining the best-fit line / curve.

3.       Be hand drawn.

4.       Include the data (a data table).


                                                  Turn over for examples.
Linear
Force is directly related to time.
If the time of travel doubled, the force needed would have to double as well.
F = 7.96 t – 6.21
Slope = 7.96 N/s. The meaning is undetermined.


                                                           Pushing a Cart With a Force Probe
                                     70
                                              y = 7.9643x - 6.2143
                                     60            2
                                                  R = 0.9993

                                     50
                         Force (N)




                                     40

                                     30

                                     20

                                     10

                                      0
                                          0                   2        4              6        8             10
                                                                           Time (s)



This is a squared relationship
Displacement is directly related to the time squared.
If the time of travel is doubled, the distance traveled will quadruple.
x = 0.996 t2


                                                 Car Traveling Down Driveway With Constant
                                                                 Acceleration

                                 250
                                                y = 0.996x2.0034
                                                       2
                                 200                   R =1
              Displacement (m)




                                 150


                                 100


                                     50


                                     0
                                          0            2           4   6         8        10       12   14        16
                                                                              Time (s)

				
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