What causes the phase lag between the displacement and the flapping of a rotor blade?

Question

Question PPL(H) - Private Pilot License - Principles of Flight (Helicopter)

QuizVDS · Accepted Answer

Inertia, mass, and aerodynamic forces

QuizVDS · Answer

Rounding of the rotor blade tips

QuizVDS · Answer

Friction in the rotor blade spindles

QuizVDS · Answer

Advance or retreat angle of 90°

Id 673 - PPL(H) EN - What causes the phase lag between the displacement and the flapping of a rotor blade?