implicit none
real mu_atm,m_keha,pi,p_atm,t_atm,g_rask,c_keha,r_atm
real s_keha,v_keha,p1,p2,p3,ro_0,x,v,t,dt,ekin,epot,etot
real a,aa,at,r_keha,ro
integer i,n
open(10,file="dim1.dat")
pi=3.1415926536
m_keha=15.
r_keha=1.8
mu_atm=29.
p_atm=100400.
t_atm=280.
g_rask=9.814
c_keha=0.47
r_atm=8314.

s_keha=pi*r_keha**2
v_keha=4.*pi*r_keha**3/3
ro_0=p_atm*mu_atm/(r_atm*t_atm)
p1=c_keha*s_keha/(2.*m_keha)
p2=g_rask*v_keha/m_keha
p3=mu_atm*g_rask/(r_atm*t_atm)
dt=0.1
v=0.
x=0.
n=50000
t=0.
do i=1,n
 t=t+dt
 ro=ro_0*exp(-p3*x)
 at=-p1*ro*abs(v)*v
 aa=p2*ro
 a=-g_rask+aa+at
 x=x+v*dt+0.5*a*dt**2
 v=v+a*dt
 ekin=0.5*m_keha*v**2
 epot=m_keha*g_rask*x
 etot=ekin+epot
 if(x<0)then
 print *,"ERROR:  x=",x,"<0"
 stop
 endif
  write (10,'(15f20.5)')t,x,v,a,at,aa,ekin,epot,etot
enddo

stop
end