In the arrangement shown, the block is slightly displaced to the right and then released.  Then time period of oscillation of the block is

(2)Effective spring constant of the system=K+K1 ×11+1=3k2When the block is displaced slightly ;ma=−3k2 ×xa=−3kx2mcomparing  with  a=−ω2xω=3k2m∴  T=2πω= 2π2m3k