A dish is made from a section of a hollow glass sphere. The dish, fixed to a horizontal table, contains a small solid ball of mass 45g, as shown in Fig. 4.1. The horizontal displacement of the ball from the centre C of the dish is x. Initially, the ball is held at rest with distance x = 3.0 cm. The ball is then released. The variation with time t of the horizontal displacement x of the ball from point C is shown in Fig. 4.2. The motion of the ball in the dish is simple harmonic with its acceleration a given by the expression a = -(g/R)x where g is the acceleration of free fall and R is a constant that depends on the dimensions of the dish and the ball. [Figure 4.1] [Figure 4.2]