Hooked on Science: Singing rod

Materials

• 2 feet, 1/4-inch aluminum rod
• Rosin

Instructions:

• STEP 1: Firmly hold the center of the aluminum rod horizontally, using the thumb and forefinger of one hand.
• STEP 2: Pinch and release a small amount of crushed rosin with the thumb and forefinger of the other hand. Describe the rosin.
• STEP 3: Gently stroke the aluminum rod from the center to the end of the rod using your rosin-coated thumb and forefinger. Repeat and slightly increase pressure of your stroking hand until you hear a high-pitched sound. Is it easy to move your finger and thumb along the aluminum rod with rosin?

Explanation:

Stroking the rod with a sticky finger and thumb, caused by the rosin, creates vibrations that travel along the length of the rod. These vibrations are transmitted to the air, creating sound waves, which eventually hit our ears, causing us to hear the unique sound.