A metal sphere of radius 
is isolated in space. Point P is a distance 
from the centre of the sphere, as illustrated in the figure below.
The variation with distance of the electric field strength 
due to the charge on the sphere is shown in the graph below.
Use the graph above to determine the radius of the sphere. Explain your working.
Use the graph above to determine the charge 
on the sphere.
An 
-particle is situated a distance 
from the centre of the sphere. Calculate the acceleration of the -particle.
.
. Therefore, the radius of the sphere is 
or 
.
.
