function fvec=free_fall_forces(x,y)
	% free fall forces example i
	% notice that physical meaning of the  independent variable 'x' is  time
	% we are solvig y''(x)=-g 
	% y1=y; y2=y'
	% f=(y2,-g);

	g=9.8; % acceleration due to free fall

	fvec(1)=y(2);
	fvec(2)=-g;
	fvec=fvec.'; % note the dot in .' this avoid complex conjugate transpose
end


