A ball is tied to an elastic string of length 8.0m and swung in a horizontal circle with a velocity if 0.8m/s. When a metallic object is tied to a rope of length 2.75m and swung in a horizontal circle, it makes 1 revolution in 2.9s. The ratio of the centripetal force in the rope is 1/3. Find the mass of the metallic object attached to the rope, if centripetal force in the string is 0.20 N.