Three particles each of mass m are located at the vertices of an equilateral triangle ABC. They start moving with equal speeds v each along the medians of the triangle and collide at its centroid G. If after collision, A comes to rest and B retraces its path along GB, then C...

According to conservation of momentum,

 

Initial momentum P_i = final momentam P_f

 

Initially all the particles were at rest.

Therefore Initial momentum P_i = 0

 

 

Hence, in order to conserve momentum, the velosity of particle C will be same as velosity of particle B but in opposite direction.

 

C will go in opposite direction of B.