haft and collar :drill bit friction :Stiffness of rotational spring :long shaft’s mass momentum of ... imulation. (use either C or Matlab only)% system dynamics 2012 spring% 2012710197 JungSeok Suhclc,c ... as torsion springA=zeros(2*N); % define A matA(1,N+1)=-1;A(2*N,N)=K/Jr;% insert repeated value to A