WM3.1 Wiffle Ball with Internal Sound Generator
Look carefully through the sides and notice the switch. Turn it on and roll around the room. For an attention getter, toss the ball to the class, but make sure they can catch it. The ball is difficult to repair. This is a qualitative analysis of the Doppler Effect. As the speed of the ball changes, the frequency changes, and so its pitch changes. Another possibility is to attach string to the ball and spin it above your head.