ISEN-ASTC-L is a service of the Association of Science-Technology Centers Incorporated, a worldwide network of science museums and related institutions. ***************************************************************************** The Song of Velocity - I just had to do it. Take a 5,000 pulse per rev shaft encoder and attach a 3 foot arm with weight at the end. Mount this assemble to a stable wall. Connect the output of the encoder to a small amplifer. One to three watts will do. Then connect to a speaker with a 8 inch or larger woofer. When you give the pendulum a push the motion is translated to a pitch. The pitch now represents velocity. Hearing the pitch and seeing the motion is a very engaging experienc for a young mind. Add stops to limit the travel of the arm. A encoder with less pulses per rev can be used but the upper limit of the pitch will be reduced. If you use a encoder with good bearings the velocity sounds will last for 3 to 5 minutes. Because the output of an encoder is a square wave even the last bit of movment can be heard. Search the surplus catalogs for a resonable priced unit. Pick a unit that has a 1/4 inch or larger shaft. This is one of those simple but effective demonstrations that have to be shared. If you need electrical or mechanical drawings let me know. Roger Sonntag - GSE - [log in to unmask] 585-338-7001 *********************************************************************** More information about the Informal Science Education Network and the Association of Science-Technology Centers may be found at http://www.astc.org. To remove your e-mail address from the ISEN-ASTC-L list, send the message SIGNOFF ISEN-ASTC-L in the BODY of a message to [log in to unmask]