Question

A block pressed against the vertical wall is in equilibrium. The minimum coefficient of friction is

• A. $0.4$
• B. $0.2$
• C. $0.5$
• D. None of these

Answer 1

The correct option is C $0.5$

Free body diagram of block can be given as

So balancing force in horizontal direction
$mg=N$
Now in vertical direction
$f+\frac{mg}{2}=mg$
where $f$ is the friction force and is given as $f=\mu N$
$\Rightarrow \mu N+\frac{mg}{2}=mg\Rightarrow \mu mg=\frac{mg}{2}\Rightarrow \mu =0.5$.