Four springs of constant as shown are attached to a pair of masses m each as shown. The time period will be 2π times
mk
2mk
4mk
3m4k
1keff =12k+12k+12k=32k⇒keff =2k3&μ=m×mm+m=m2.T=2πμkeff=2πm2×2k3⇒T=2π3m4k