Hi Jan -- I'll take a stab at it... I don't know anything about your level of knowledge of math and physics, and the following may be too elementary or too complex, but please let me know if you want more explanation. Take a string about 3 feet long and tie a weight at one end (a shoe would work). Hold the string by the other end and let the weight dangle down without hitting anything. Then have someone pull the weight a bit to the side (keeping the string taut) and let it go. It will swing back an forth, and the time it takes it to go from one end over and back to the same place again is the period. The period of a simple pendulum (one with only one weight on it and a string that weighs little compared to the weight, is given by the following equation: T = 2 * pi * sqrt(L / G) The variables are: T is time in seconds, pi is the constant 3.14159... , sqrt is an abreviation for square root, L is the length of the string from the pivot to the center of mass of the weight, and G is the acceleration of gravity. If L is expressed in inches, the acceleration of gravity should be 386.1 inches per second squared. You really don't need to worry about the units if you use the length in inches, and use 386.1 for gravity. For example, use a length of 30 inches. Take 30 and divide it by 386.1 to get 0.0777. Take the square root of that to get 0.2787. Then multiply the result by 3.14159 and result of that by 2, to get 1.751 second. So a 30" long pendulum will take about 1.75 seconds to swing over and back to the same place. That is its period. When making a seismometer the longer the period of the pendulum the longer the period of the waves that can be measured. Usually, this is desireable. Regards, Karl Cunningham --On Friday, October 05, 2001 21:53 -0600 "Jan D. Marshall"
wrote: > Could some one give me a quick 101 course on what is ment by the > "period of the pendulum" how does that relate to a seismograph, > what period are we striving for? __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>