a good question

Its is obvious 4 electrostatic force but 4 gravitational force.....

let me see....

A similar theory for gravitational flux.....
will prove that.

total flux crossing an enclosed surface is 4piGm

m is mass enclosed here it is zero so flux is zero so ∫E.dS=0
here E=0.....

Ne one has some other method...........

but i have the same method with a totalyyyyyyyyyyyyyyyyyyyyyyyyyyy different approach

[the sought force of attraction is the geometrical sum of the forces created by the separate elements of the sphere.the small elements σ1 and σ2 are cut out of the sphere as cones with vertices at point A obtained when the generatrix BC revolves around the axis S1S2. The areas of the elements are (AS1).(AS1)ω/COSα1 and (AS2)(AS2)ω/COSα2 RESPECTIVELY and their masses are (AS1)(AS1)ωρ/COSα1 AND (AS2)(AS2)ωρ/COSα2 ;where ω is the solid angles at which both the elements can be seen from the point A;ρ IS THE MASS PER UNIT OF SURFACE THE SPHERE.

now, α1=α2 since S1OS2 is an isosceles triangle.the forces of attraction created by the sphere are equal,respectively to

γmρω/cosα1 and

γmρω/cosα2 where `m` is the mass of the body.these forces act in opposite direction and their resultant is zero.

reasoning in the same way for all the other corresponding elements of the of the sphere,we can say that all of them compensate one another in pairs.

therefore the force of attraction acting from the sphere on the body is zero.

S1OS2 is an isosceles triangle.????

have u taken A as a general pt. then how cum isosceles?