As shown below

mass_spring_03052020/calculation.mclear all;
clc;
M = eye(3);% Assu;ming mass is unit function
k = 0.01*[2,-1,0;-1,2,-1;0,-1,1]; % Stiffness matrix;
c = k;% Assumption that c = k;
[V,D] = eig(k,M);% Finding eigen value and eigen vector for the calculation
F = V'*[1;1;1];
% Open Loop...