question_answer

A highly rigid cubical block \[A\] of small mass \[M\] and side \[L\] is fixed rigidly onto another cubical block \[B\]of the same dimensions and of low 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 After the force is withdrawn block \[A\] executes small oscillations. The time period of which is given by                [IIT 1992]

A)    \[2\pi \sqrt{\frac{M\eta }{L}}\]

B)             \[2\pi \sqrt{\frac{L}{M\eta }}\]

C)     \[2\pi \sqrt{\frac{ML}{\eta }}\]

D)                      \[2\pi \sqrt{\frac{M}{\eta L}}\]