A solid sphere of uniform density and radi

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A solid sphere of uniform density and radius $4$ units is located with its centre at the origin $O$ of coordinates. Two spheres of equal radii $1$ unit with their centres at $A(-2, 0, 0)$ and $B(2, 0, 0)$ respectively are taken out of the solid leaving behind spherical cavities as shown in figure

A

The gravitational force due to this object at the origin is zero

B

The gravitational potential is the same at all points on the circle ${y^2} + {z^2} = 4$

C

The gravitational potential is the same at all points of the circle ${y^2} + {z^2} = 36$

D

All of the above

A solid sphere of uniform density and radius $4$ units is located with its centre at the origin $O$ of coordinates. Two spheres of equal radii $1$ unit with their centres at $A(-2, 0, 0)$ and $B(2, 0, 0)$ respectively are taken out of the solid leaving behind spherical cavities as shown in figure

Since cavities are symmetrical w.r.t. $O$. So the gravitational force at the centre is zero. 

The radius of the circle ${z^2} + {y^2} = 36$ is $6$.

For all points for $r \ge 6,$ the body behaves as if whole of the mass is concentrated at the centre. So the gravitational potential is same. 

Above is true for ${z^2} + {y^2} = 4$ as well.