A pendulum bob has mass m .The length of the pendulum is f. It is initially at rest. A particle P of mass m/2 moving horizontally along -ve x-direction with velocity root(2gf) collides with the bob and comes to rest momentarily, another particle Q of mass m moving horizontally long z-direction collides with the bob and stick to it. It is observed that bob now move in horizontal circle. The floor is a horizontal surface at a distance2l below the point of suspension of the pendulum.