A thin spherical shell having uniform density is cut in two parts by a plane and kept separated as shown in figure (11-E3). The point A is the Centre of the plane section of the first part and B is the Centre of the place section of the second part. Show that the gravitational field at A due to the first part is equal in magnitude to the gravitational field at B due to the second part.
To solve this, we first assume that the two parts are joined to form a complete spherical shell. This helps us to find field when we break the conic. Now, we know that the field inside the shell is zero. Let the gravitational field at A due to the first part be E and the gravitational field at B due to the second part be E’.
Therefore, 
Hence, the fields are equal is magnitude and opposite in direction