Answer:
Acceleration is defined as the ratio between the change in velocity of an object and the time it takes for the object to change the velocity.
In formula, this is written as:

where
vf is the final velocity
vi is the initial velocity
t is the time it takes for the object to accelerate from u to v
Note that acceleration is a vector, so it can also be caused by a change in the direction of the velocity, not only by a change in its magnitude.
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Answer:
at r < R;
at 2R > r > R;
at r >= 2R
Explanation:
Since we have a spherically symmetric system of charged bodies, the best approach is to use Guass' Theorem which is given by,
(integral over a closed surface)
where,
= Electric field
= charged enclosed within the closed surface
= permittivity of free space
Now, looking at the system we can say that a sphere(concentric with the conducting and non-conducting spheres) would be the best choice of a Gaussian surface. Let the radius of the sphere be r .
at r < R,
= 0 and hence
= 0 (since the sphere is conducting, all the charges get repelled towards the surface)
at 2R > r > R,
= Q,
therefore,
(Since the system is spherically symmetric, E is constant at any given r and so we have taken it out of the integral. Also, the surface integral of a sphere gives us the area of a sphere which is equal to
)
or, 
at r >= 2R
= 2Q
Hence, by similar calculations, we get,
