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:
1
\(\frac{GMm\pi}{2L^2}\)
2
0
3
\(\frac{GMm\pi^2}{L^2}\)
4
\(\frac{2GmM\pi}{L^2}\)