Two particle of mass m each are tied at the ends of a light string of length 2a. The
whole system is kept on a frictionless horizontal surface with the string held tight so
that each mass is at a distance ‘a’ from the center P (as shown in the figure). Now, the
mid-point of the string is pulled vertically upwards with a small but constant force F. As
a result, the particles move towards each other on the surface. The magnitude of
acceleration, when the separation between them becomes 2x is