i have solved a torsional semi-definite system problem. i have uploaded the solved problem. solved for modal participation factor and effective mass. for a semi definite system we know that one of the modes is rigid mode with natural frequency 0. i think due to the presence of rigid mode i'm getting the modal participation factor vector as [5.3157 -3.76* 10^-3]. is this answer right? i mean how can there be no contribution from the flexible mode?