Question

$A$ body $B$ lies on a smooth horizontal table and another body $A$ is placed on $B$. The coefficient of friction between $A$ and $B$ is $\mu$. What acceleration given to $B$ will cause slipping to occur between $A$ and $B$?

• A. $\frac{\mu }{g}$
• B. $\sqrt{\mu g}$
• C. $\frac{\mu }{m}$
• D. $\mu g$

Answer 1

The correct option is D $\mu g$

Draw $FBD$ of both the blocks

Let applied force be $F$ on lower block
Let $f$ be friction acting towards right on upper block and leftwards on lower block

Find acceleration given to block $B$
Upper block has only friction acting on it and maximum acceleration block $A$ can have is
$\frac{f}{m}=\frac{\mu mg}{m}=\mu g$
$\therefore$ Acceleration of lower block will be more than $\mu g$ to make upper block slip on lower block

Final answer: Option (a)