A charge of +80 mC is placed on the x axis at x = 0. A second charge of -50 mC is placed on the x axis at x = 50 cm. What is the magnitude of the electrostatic force on a third charge of 4.0 mC placed on the x axis at x = 30 cm?

Answer 1

pushed right by the first, sucked right by the second
F = k (4*10^-3) [ 80*10^-3 / 0.3^2 + 50^-3 / 0.5^2 ]

Answer 2

F = k (4*10^-3) [ 80*10^-3 / 0.3^2 + 50^-3 / 0.2^2 ]