1. The problem statement, all variables and given/known data The diagram shows two charged spheres X and Y, of masses 2m and m respectively, which are just prevented from falling under gravity by the uniform electric field between the two parallel plates. If the plates are moved closer together A X and Y will both remain stationary. B X and Y will both move upwards with the same acceleration. C X will have a greater upward acceleration than Y. D Y will have a greater upward acceleration than X. (I haven't posted the diagram, but it just shows 2 plates lying horizontally with 2 circles directly in the middle of the 2 plates, one circle twice the size of the other) 2. Relevant equations F = eq F = ma E = V/D 3. The attempt at a solution The answer is B, but I don't understand why. Plates moved closer together, E=V/D, so electric field increases in strength. I understand that in a gravitational field the only force is W=mg, so F=W so ma = mg, g's cancel so a is constant. But in a gravitation field surely F=eq so eq=ma so a = eq/m. In other words, suerely mass would have an effect on the upwards acceleration? So the upwards acceleration of both would not be equal?