f(x) = 6.28319 * sqrt(x / 9.81)
P_1 = (0.1, 0.63)
P_2 = (0.2, 0.9)
P_3 = (0.3, 1.1)
P_4 = (0.4, 1.26)
P_5 = (0.5, 1.42)