function dotq = square_object_free_param( t, q, npoint, M, B, K, force )
% ‰^“®•û’öŽ®�iŽ©—R‰^“®�j
    u = q(1:npoint*2);
    v = q(npoint*2+1:npoint*4);
    
    dotu = v;
    
    mat = M;
    vec =-K*u -B*v + force(t,npoint,u,v);
    sol = mat\vec;
    dotv = sol(1:npoint*2);
    
    dotq = [dotu; dotv];
end
