​

function setup() {

  createCanvas(400, 400);

  //https://en.wikipedia.org/wiki/Foucault_pendulum

  m=2;l=2.8415;phi=-(50+5/60)/360*2*PI;g=9.813 //WP@Prague

  //m=28;l=67;phi=-(48+52/60)/360*2*PI;g=9.832 //Pantheon@Paris

  //m=28;l=67;phi=(0)/360*2*PI;g=9.780 //Pantheon@Equator

  //m=28;l=67;phi=(90)/360*2*PI;g=9.832 //Pantheon@Pole

  //m=100;l=18.5;phi=(33+27/60)/360*2*PI;g=9.832 //FCFM Santiago de Chille

  Omega=2*PI/(24*60*60) //the rotational frequency of the Earth

  i=0;t=0;FPS=25;dt=1/FPS;x=1;vx=0;y=0;vy=0 //initials

  omega2=g/l

  Interval=60 //seconds

  writer = createWriter('WP@Prague_60s.dta');

}

​

function draw() {

  //background(220);

  //Coriolis force

  Fcx=2*m*Omega*vy*sin(phi);Fcy=-2*m*Omega*vx*sin(phi)

  //The restoring force, in the small-angle approximation

  Fgx=-m*omega2*x;Fgy=-m*omega2*y

  ax=(Fgx+Fcx)/m;ay=(Fgy+Fcy)/m

  //Euler

  vx=vx+ax*dt;vy=vy+ay*dt

  x=x+vx*dt;y=y+vy*dt

  i=i+1;t=t+dt

  writer.write([i,t,x,y,'\n']);  

  ppm=150;circle(x*150+200,y*15000+200,1) //! x and y not in the same scale !

  if (t>Interval) //Konec

    {

      writer.close();

        noLoop()

    }

}