Question 168 of 210

The coefficient of static friction between a wooden block of mass $0.5kg$ and a vertical rough wall is $0.2.$ The magnitude of the horizontal force that should be applied on the block to keep it adhere to the wall will be______$N$. $\left⌈g=10m{s}^{-2}\right]$

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Answer: 25

$F.B.D.$ of the block is shown in the diagram

Since block is at rest therefore
$fr-mg=0...\left(1\right)$
$F-N=0...\left(2\right)$
$fr\leq \mu N$
In limiting case
$fr=\mu N=\mu F\ldots \left(3\right)$
Using eq. $\left(1\right)$ and $\left(3\right)$
$∴\mu F=mg$
$\Rightarrow F=\dfrac{0.5\times 10}{0.2}=25N$