VI. BALL VIBRATIONS
An estimate of the losses due to vibrations induced in the
tennis ball was obtained by gluing a small (4mm34mm!
piezoelectric ceramic element, of thickness 0.3 mm, onto a
tennis ball and measuring the induced voltage by means of
light wires soldered onto the element. Results are shown in
Fig. 6 for a case where the ball was dropped from a height of
10 cm onto the 50 mm diam piezo. When the small piezo
element is located near the bottom of the ball, the force wave
form observed is similar to that observed with the large piezo