A block weighs $W$ is held against a vertical wall by applying a horizontal force $F$. The minimum value of $F$ needed to hold the block is
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(c) Here applied horizontal force $F$ acts as normal reaction.
For holding the blockForce of friction = Weight of block
$f = W$ $⇒$ $\mu \,R = W$ $⇒$ $\mu \,F = W$
$⇒$ $F = \frac{W}{\mu }$ As $\mu < 1$
$\therefore \;\;\;F > W$
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