A metal wire of uniform mass density having length \( L \) and mass \( M \) is bent to form a semicircular arc and a particle of mass \( m \) is placed at the centre of the arc. The gravitational force on the particle by the wire is:
\( \dfrac{2 G M m \pi}{L^{2}} \)
\( 0 \)
\( \dfrac{G M m \pi^{2}}{L^{2}} \)
\( \dfrac{G M m \pi}{2 L^{2}} \)
