function [ dX ] = CartDynamics( X, F, T )
%cart dynamics  
% cart = 2kg
% ball = 1kg
% length = 1m
% X = [x, q, dx, dq]
x = X(1);
q = X(2);
dx = X(3);
dq = X(4);
g = 9.8;
M = [3 cos(q); cos(q), 1];
A = [dq*dq*sin(q); g*sin(q)];
BF = [1;0];
BT = [0;1];
d2X = inv(M) * (A + BF*F + BT*T);
dX = [dx; dq; d2X];
end