I am indeed having fun . . . combining two loves; RR scripting and Physics.Roger, There is a real catch in solving the Foucault Pendulum problem. The equations of motion have no closed form solution. (Although there are approximate solutions for small amplitude and for small angular velocity.) But if you employ the method illustrated in the Turtle Graphics Demo you don't need the solution, you effectively solve the equations of motion with a very simple algorithm:repeat xNew = xOld + velocityOld*t velocityNew = velocityOld + acceleration*t (put the new x into the old x and draw the line) (put the new velocity into the old velocity) end repeat where t is some fixed small time increment, and the acceleration is a known function. If for simplicity you take t = 1 (sec), the TG code for *any* problem in dynamics is: Repeat forever --Or until you lose patience IncrementXY vx, vy add accx() to vx add accy() to vy end repeat The line "IncrementXY vx,vy" increments the x and y coordinates of the path by vx and vy, and simultaneously draws the line. It doesn't get much simpler. This becomes a template for solving *all* such problems in dynamics. You just have to write different acceleration functions depending on the physical circumstances. You can see why I am promoting Transcript/TG as a mean of teaching programing to high school science students. This algorithm is in effect the solution to the differential equation of motion by the method of finite differences, but I wouldn't tell anybody--they will shun you. May I suggest the two dimensional harmonic oscillator rather than the Foucault Pendulum. You get beautiful Lissajou figures (prettier than the Foucault path) which are open or closed depending on the ratio of the x and y spring constants. This is a very rich problem for exploration. Good luck. You look like you are having fun. Jim
Cheers, Roger
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