mechanics doubty!

no one is replying to queries.......... :( ...........seems TIIT is haunted

this one was solved by sir long time back,......try to find it...

find the initial potential energy.
the system gains some velocity and at some moment the velocity of both the particles is zero, i.e KE=0 (at θ=θ_max)

equate initial PE to PE at θ=θ_max..... u get the ans.
θ≈127⁰... i think