Since, the three springs with spring constants k,k and 2k are attached to the mass m in parallel. So, net spring constant =k+k+2k=4k ∴ The net restoring force on mass m, ∣Fnet ∣=−4kx
As, force in SHM, ∣FSHM∣=−mω2x
On comparing Eqs. (i) and (ii), we get mω2=4k ω=m4k T=ω2π=2π4km