Why does pseudo force act in opposite directions when we move from ground frame to the centre of mass?

By | July 12, 2018

enter image description here In the solution of above question, they solved it by moving from ground frame to the frame of centre of mass. But we know that, to move from one frame to another ,we have to subtract the mass-acceleration product. But in the above case, pseudo force is applied in two opposite direction. Is their any other approach to solve it from ground frame?