You have two small, 2.0 g balls that have been given equal but opposite charges, but you don’t know the magnitude of the charge. To find out, you place the balls distance d apart on a slippery horizontal surface, release them, and use a motion detector to measure the initial acceleration of one of the balls toward the other. After repeating this for several different separation distances, your data are as follows:

Distance (cm)  Acceleration (m/s²)
2.0 ...............................................0.74
3.0 ...............................................0.30
4.0 ...............................................0.19
5.0 ...............................................0.10

Use an appropriate graph of the data to determine the magnitude of the charge.