The centres of two charged metal spheres A and B are separated by a distance of 
, as shown in the figure below.
A moveable point P lies on the line joining the centres of the two spheres. Point P is a distance 
from the centre of sphere A. The variation with distance of the electric potential 
at point P is shown in the graph below.
Use the graph above to state and explain whether the two spheres have charges of the same, or opposite, sign.
A positively-charged particle is at rest on the surface of sphere A. The particle moves freely from the surface of sphere A to the surface of sphere B.
Describe qualitatively the variation, if any, with distance x of the speed of the particle as it moves from 
to 
, passes through 
, moves from 
to 
and reaches 
.
The particle has charge 
and mass 
. Calculate the maximum speed of the particle.
.
