k = [1,2,3];
T = 1;
ksi = [0.707, 0.5, 0.3]; % 0<ksi<1
tfin = 15;

for i = 1:3
    for j = 1:3
        sysk = tf(k(i), [T*T, 2*ksi(j)*T, 1]);
        figure(4);
        impulse(sysk, tfin);
        grid on;
        hold on;
        'press a key';
        pause;
    end
end
hold off;