Doppler Nerf Ball

PIRA 3B40.10

The 9 V battery and buzzer shown at left can be stuffed inside the nerf ball and taped closed.  Play catch with students to demonstrate the Doppler effect.  It must be thrown fairly fast for the Doppler shift to be noticeable.

The elastic strap and string shown at left can be attached, allowing the ball to be swung in a circle.