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)
F = eq
F = ma
E = V/D
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?