Hooked on Science: Make an aluminum rod sing

Using a few materials from around the house you can make a sound by creating friction between your fingers and an aluminum rod.

Materials

* Aluminum rod

* Rosin

Instructions

STEP 1: Rub the rosin on your pointer finger and your thumb.

STEP 2: Pinch the rod with the other hand at exactly the middle point and hold the rod into the air.

STEP 3: Gently stroke the aluminum rod from the center to the end of the rod using your rosin-coated fingers. Repeat and slightly increase the pressure of your stroking hand until you hear a high-pitched tone.

Explanation

When you hold the aluminum rod in the center and stroke it with rosin-coated fingers, your fingers slip and stick as they slide. This causes the rod to start moving with one of its natural frequencies of vibration -- a half-wave tone.

Jason Lindsey is a science outreach educator with Hooked on Science. Check out his website www.hookedonscience.org for webcasts and experiments.