#!/home/misha/venv/bin/python
import numpy as np
import matplotlib.pyplot as plt
import scipy.integrate as ode

g_rask=9.814
r_keha=1.8
s_keha=np.pi*r_keha**2
c=0.47
v_keha=4.*np.pi*r_keha**3/3
m_keha=15.

p_atm=100000.
t_atm=293.
mu_atm=29.
R=8314.

ro_atm_0=p_atm*mu_atm/(R*t_atm)
p1=g_rask*mu_atm/(R*t_atm)
p2=0.5*c*s_keha/m_keha
p3=g_rask*v_keha/m_keha
def func(y,t):
   yp=np.zeros_like(y)
   yp[0]=y[1]
   ro=ro_atm_0*np.exp(-p1*y[0])
   v=np.abs(y[1])
   yp[1]=-g_rask-p2*ro*v*y[1]+p3*ro
   return yp

y0=[0.,0.]
time=np.linspace(0,5000,num=10000)
res=ode.odeint(func,y0,time)

fig,[p1,p2]=plt.subplots(1,2)
p1.plot(time,res[:,1])
p2.plot(time,res[:,0])
p1.grid()
p2.grid()
plt.show()