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 ?

Explanation

If we assume that the particles are initially at the mean position, their equation for displacement
`x= A sin omega t `
But `x = A/2`
`therefore A/2 = A sin omega t ` (or) `sin omega t = 1/2`
Phase `=omega t = 30^@ , 150^@`
`(because sin (180^@ - theta) = sin (180^@ - 30^@) = sin 30^@)`
One of the particles has phase of `30^@` and the other has phase of `150^@`
Phase difference between them `=120^@ = (2pi)/(3)` radian.