Pith ball lab. HELP In the lab there are 2 balls that are being seperated by an electrostatic force. Since both of the balls are receiving the same force it is only neccesary to find the force on one of the balls. So here goes. The formula I am using is Fe=k q/r(squared) I know k= 9.0 x 10^9 R= 7.3 cm or .073m and the angle is 20* for one side I believe I need to find tension in the string. And find the horizontal component so I can find Fe because those 2 are equivalant. I am just not sure how to do it. :uhh: Thanks for the help!