Question

A block $P$ of mass $m$ is placed on a frictionless other block $Q$ of same mass is kept on $P$ and connected to the wall with the help of a spring of spring constant $k$ as shown in the figure. $\mu_{ s }$ is the coefficient of friction between $P$ and $Q$. The blocks move together performing SHM of amplitude $A$. The maximum value of the friction force between $P$ and $Q$ is:

• A. k A
• B. $\frac{k A}{2}$
• C. zero
• D. $\mu_{s} m g$

Answer 1

Answer: (B)

$f_{\max }=m \omega^{2} A$
With $\omega^{2}=\frac{k}{m+m}=\frac{k}{2 m}$
Hence, $f_{\max }=m\left(\frac{k}{2 m}\right) A=\frac{k A}{2}$