statistics

A smooth circular hoop with a radius of 0.400 m is placed flat on the floor. A 0.425-kg particle slides around the inside edge of the hoop. The particle is given an initial speed of 7.00 m/s. After one revolution, its speed has dropped to 4.00 m/s because of friction with the floor. (a) Find the energy transformed from mechanical to internal in the particle-hoop-floor system as a result of friction in one revolution. (b) What is the total number of revolutions the particle makes before stopping? Assume the friction force remains constant during the entire motion