z1

m = 1

v0 = 20

g = 9.8

r = 0.1

dt = 0.001

t = 0

y, v = [], []

y.append(0)

v.append(v0)

i = 0

while y[i] >= 0:

  y.append(y[i] + dt * v[i])

  v.append(v[i] + dt * (-g - r * v[i] / m))

  i += 1

  t += dt

print(max(y), t)