A thin wire of length L and mass M  is bent to form a semicircle. What is the gravitational field at the centre.

$\pi GM/L^2$  among the line joining the ends

$\pi GM/L^2$ perpendicular to the above line.

 $2\pi GM/L^2$ along the line joining the ends.

$2\pi GM/L^2$ perpendicular to the above line.