This problem was contributed by Sukumar Chandra.
Three small balls of masses m, 2m and 3m are placed on a smooth horizontal surface so that they lie on the vertices of an equilateral triangle. The masses m and 2m, as well as 2m and 3m, are connected by light inextensible strings. Initially the strings are taut and the mass m is given a velocity v on the surface in a direction parallel to the string connecting 3m and 2m. With what velocity does mass 3m eventually starts moving? (Neglect friction and the mass of the strings.)
Answer :