A stick of mass m and length L is pivoted at an end. It is held horizontal and then released. It swings down, and when it is vertical the free end elastically collides with a ball. (Assume that the ball is initially held at rest and then released a split second before the strick strikes it.) If the stick loses half of its angular velocity during the collision, what is the mass of the ball? What is the speed of the ball right after the collision?