Two stones of masses m and 2m are whirled in horizontal circles, the heavier one in a radius $${r \over 2}$$ and the lighter one in radius r. The tangential speed of lighter stone is n times that of the value of heavier stone when they exprience same centripetal forces. The value of n is

Three blocks A, B and C, of masses 4 kg, 2 kg and 1 kg respectively, are in contact on a frictionless surface, as shown. If a force of 14 N is applied on the 4 kg block, then the contact force between A and B is

A block A of mass m₁ rests on a horizontal table. A light string connected to it passes over a frictionless pully at the edge of table and from its other end another block B of mass m₂ is suspended. The coefficient of kinetic friction between the block and the table is $$\mu $$_k. When the block A is sliding on the table, the tension in the string is

A balloon with mass m is descending down with an acceleration a (where a < g). How much mass should be removed from it so that it starts moving up with an acceleration a ?