Q. A block weighing $W$ is held against a vertical wall by applying a horizontal force $F$. The minimum value of $F$ needed to hold the block is
A) Less than $W$
B) Equal to $W$
C) Greater than $W$
D) Data is insufficient
Explanation
(c) Here applied horizontal force $F$ acts as normal reaction. For holding the block
Force of friction = Weight of block
$f = W \Rightarrow \mu\ R = W$
$\Rightarrow \mu F = W$
$\Rightarrow F = \frac{W}{\mu}$
As $\mu < 1\ \therefore F > W$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.