4 Step Analysis
As an example lets take a graph from the BPV lab. The slope is .25m/s and
the y-int. is .0115 m
X
(m)
T (s)
1. Start with the general equation for a line
Y = MX + b
2. Substitute the variables from your graph into the equation
X = .25m/s T + 0.0115 m
3. To ‘b’ or not to ‘b’. Is the y-int significant or not? Here is how we decide:
b/ymax x 100 = ______ %
take your b value and divide it by the largest Y value in your data table
and multiply by 100 to get a percent. If your value is less than 5% then
you may drop the y-int. If your answer is greater than 5% OR if we
discussed the significance of the intercept during the lab, then keep b.
For example, our b value is 0,0115m and the largest position value from
the data table is 5.0m. Then 0.0115/ 5.0 = 2.3% which is less than 5% so
we drop the y-int from the equation.
4. Write the final equation dropping the y-int (if necessary)
X = .25m/s T