A bead 'B' of mass m is attached to one end of a spring(AB) of natural length R and spring constant K= (√3+1)mg/R. The normal reaction at B just after it is released to move is:
mg
Extension in the spring is
x=AB−R=2Rcos 30∘−R
=(√3−1)R
Spring force
F=kx=(√3+1)mgR×(√3−1)R = 2mg
From figure N = = (F + mg)cos 30∘ = x√3 mg2