The gravitational potential at the centre of base of a solid hemisphere of mass M and radius R

I hope this information will help you...
The gravitational potential is constant at all points inside a sphere.
V=Constant
So, dV/dr=0
i.e. the gravitational potential gradient at all points inside it will be zero.
Now,
Gravitational intensity=- (dV/dr)
Thus, gravitational intensity will be zero at all points and also at the centre.....