c
c Fortran code to simulate identical particle positions
c		from constant velocities
c		in both non-rotating (inertial) and
c		rotating systems of reference
c
c compiles on MacBook Pro (Mid 2015) under macos 12.7.2
c		with GNU Fortran (Homebrew GCC 13.2.0)  13.2.0
c
c Feb.-9, 2024 Andreas Muenchow, University of Delaware
c
	real u0,v0,x0,y0,t,pi,arg
c m/s
	u0 = 10
	v0 = 0.
c m
	x0 = 0.
	y0 = 5
c
c Period of Rotation in seconds
	P = 5
	pi = 4*atan2(1.,1.)
c
c Frequency of rotation
c
	omega = 2*pi/P
c second
	dt = 0.1
	do 1 i=1,200
	   t = (i-1)*0.1-10
	   arg = omega*t
	   ccos = cos(arg)
	   ssin = sin(arg)
c
c Particle Position in non-rotating system
c
	   xfix = x0+u0*t
	   yfix = y0+v0*t
c
c Particle Position in rotating system
c
	   x = +xfix*ccos+yfix*ssin
	   y = -xfix*ssin+yfix*ccos
c ignore 
	   u =  u0*ccos-omega*(xfix*ssin-yfix*ccos)
	   v = -u0*ssin-omega*(xfix*ccos+yfix*ssin)
c plotted
	   write(7,101)t,x,y,xfix,yfix
101	   format(5f10.3)
1	continue
	write(6,*)'Done'
	stop
	end