Two particles execute SHM of same amplitude and frequency on parallel lines. They pass one another when moving in opposite directions each time their displacement is one thhird their amplitude. What is the phase difference between them?

Two particles execute SHM of same amplitude and frequency on parallel lines. They pass one another when moving in opposite directions each time their displacement is half of their amplitude. What is the phase difference between them?

Two particles execute SHM of the same amplitude and frequency on parallel side by side. They cross each another when moving in opposite directions each time their displacement is half their amplitude What is the difference between them ?