Q. A highly rigid cubical block $A$ of small mass $M$ and side $L$ is fixed rigidly on to another cubical block of 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 After the force is withdrawn, block $A$ executes small oscillations, the time period o which is given by
A) $2\pi\sqrt{M\eta L}$
B) $2\pi\sqrt{\frac{M\eta}{L}}$
C) $2\pi\sqrt{\frac{ML}{\eta}}$
D) $2\pi\sqrt{\frac{M}{\eta L}}$
Explanation
$\lbrack\eta\rbrack = \lbrack ML^{- 1}T^{- 2}\rbrack$or [$T$]=$\left\lbrack \frac{M}{L\eta} \right\rbrack^{1/2}$ Time period $= 2\pi\sqrt{\frac{M}{L\eta}}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.