Sorry here is the complete question:
Figure 1 shows a negative ion which has a charge of -3e and is free to move in a uniform electric field. When the ion is accelerated by the field through the distance of 63mm parallel to the field lines it's kinetic energy increases by 4.0 x 10^-16J.
Calculate the magnitude of the electrostatic force acting on the ion?
Not sure what to do if your given kinetic energy, it just seems confusing, the sia gram just shows field lines and the point charge of -3e
Thanks