A highly rigid cubical block `A` of small mass `M` and side `L` is fixed rigidly on the other cubical block of same dimensions and of modulus of rigidity `eta` such that the lower face of `A` completely covers the upper face of `B`. The lower face of `B` is rigidly held on a horizontal surface . `A` small force `F` is applied perpendicular to one of the side faces of `A`. After the force is withdrawn , block `A` executes faces of `A`. After the force is withdrawn , block `A` exceutes small oscillations , the time period of which is given by

Options

A. ` 2 pi sqrt(M eta L)`
B. ` 2 pi sqrt(M eta //L)`
C. ` 2 pi sqrt(M L //eta )`
D. ` 2 pi sqrt(M //eta L)`

Answer

D

Explanation

`[eta] = [ ML^(-1) T^(-2)]`
Hence , `[sqrt((M)/(eta L))] = sqrt (([ M ])/[(ML^(-1) T^(-2)] [L])) = [T]`