Two identical spheres, each of mass m are suspended by vertical strings such that they are in contact with their centres at the same level. A third identical sphere strikes the other two spheres simultaneously with a velocity U such that the centres of the spheres at the instant of impact form an equilateral triangle in a vertical plane. If the collision is perfectly elastic, then the combined impulse due to the strings is

Options

A. `(12)/(7)m u`
B. `(6)/(7)m u`
C. `(2sqrt3)/(7) m u`
D. `(8)/(7)m u`

Answer

A