ball in each frame of the video.

$4.$ Your measurements need to be converted to meters. If your video analysis software is not set up to do this automatically, figure out how to do it$.$

$5.$ Set up calculated columns in the video analysis software or a spreadsheet to calculate the Coulomb force $F_e$ from your data for $x_{\text{b}\text{a}\text{l}\text{l}},$ and also to calculate $r,$ the distance between the suspended ball and the prod ball from your data for $x_{\text{b}\text{a}\text{l}\text{l}}$ and $x_{\text{p}\text{r}\text{o}\text{d}\text{.}}.$