Standing Waves

So this weekend I was playing with my guitar when I looked a little closer at the strings. Every time I plucked one it would create a wave. Not only that the wave had two nodes on each end and one anti-node in the middle. This standing wave has a base frequency of an E at 82.41 Hz. This is the frequency of nothing touching the surface and just a wave produced by plucking the string. By lightly touching the string at its bisector you can create a node there and produce its first harmonic frequency. You can actually repet this for 4 more hamonic frequencies on this string. All you have to do is go to a position with a node of a harmonic frequency and then touch it to create a node there. Instead of the string vibrating at a certain speed and increasing the speed you are imposing a node at certain points changing the length rather than the velocity.

Thanks for reading, Mark.

Pan-Pacific Championchip

This past weekend was the Pan-Pacific Tournament for the Vex Robotics Competition. This means that everyone across the pacific and California was able to meet and fight to see who had the best robot for the 2008-2009 Elevation challenge. This competition was a very good representation of the concept of friction. As you can see through this video, the wheels of each robot requires the friction of the foam mat to push back so the wheels don’t skid. This creates the forward force on the robot moving it forward. The cubes work the same way. The treads on the robots wouldn’t pick up the cube without the extra friction created through the normal force exerted by the zip-ties and parallel tread. The cube exhibits cooler interactions when placed into the triangular goal. It touches the sides decelerating the corner but not the rest of the cube. This causes the cube to rotate as it falls. Without friction this competition could be really cool but it would also make it almost impossible to stop, turn, or even start.

Thanks for reading, Mark.

At this competition team 2438 (Iolani) and 687j and 687k placed first overall.