Essentially, each journey of the ball from floor to wall to floor, assumed to take place in the same vertical plane, comprises four events: (i) after launch from the floor the ball pursues a parabolic trajectory until it hits the wall, (ii) the rebound from the wall, (iii) the parabolic trajectory of the return journey to the floor and (iv) the impact with the floor which provides the launch data for the next excursion of the ball