function y = x2dot(x)
F =  x(1);
x3 = x(2);
x4 = x(3);
g = 10 ; % percepatan gravitasi 10 m/sec2
l = 0.6 ; % panjang batang 60 cm
M = 0.25 ; % Massa kereta 250 gr
m = 0.025 ;