Three small balls of equal mass (m) are suspended from a thread and two springs of same force constant (K) such that the distances between the first and the second ball and the second third ball are the same. Thus the centre of mass of the whole system coincides with the second ball. The thread supporting the upper ball is cut and system starts a free fall. Find the distance of the centre of mass of the system from the second ball when both the springs acquire their natural length in the falling system.

Answer

`(mg)/(3K)`