Mode2入2=±1.85i M M M2 Middle frequency mode has middle mass moving in opposition to two end masses Again middle mass has higher amplitude motions 23 V3• Mode 2 λ2 = ±1.85i M1 M3 M2 -  - – Middle frequency mode has middle mass moving in opposition to two end masses – Again middle mass has higher amplitude motions z3 0 1 2 3 4 5 6 7 8 9 10 −0.4 −0.3 −0.2 −0.1 0 0.1 0.2 0.3 0.4 time displacement V3 z1 z2 z3 3