import math
def meteor(n):
r = .09
m=7
b=1.5e-3
x = 200.*1000.
v = -20.*1000.
H = 7.6*1000.
g = 9.8 # m/s2
t_max = -x/v*10.
dt = t_max/n
for i in range(n):
dx = v*dt
x = x+dx
if x<0.:
return v
F = b*v**2*math.exp(-x/H)-m*g
a = F/m
dv = a*dt
v = v+dv
return -999
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