2 DOF

Question 1

what is a mode shape? (simple terms)

Answer 1

describes the relative motion of the 2 oscillation coordinates

Question 2

2 important features for 2 DOF

Answer 2

2 natural frequencies (eigenvalues)
mode shapes (eigenvectors)

Question 3

mode shapes

Answer 3

describe the relative amplitudes in the system when it oscillates at one of the natural frequencies.
can also be seen as initial conditions which cause both coordinates to oscillate at the same natural frequency.