Search any question & find its solution
Question:
Answered & Verified by Expert
A block of mass $M$ is held against a rough vertical wall by pressing it with a finger. If the coefficient of friction between the block and the wall is $\mu$ and the acceleration due to gravity is $g$, calculate the minimum force required to be applied by the finger to hold the block against the wall.
Solution:
1375 Upvotes
Verified Answer
As given that, mass of the block $=M$
Coefficient of friction between the block and the wall $=\mu$.
Let $F$ force be applied by finger on the block to hold the block against the wall. The nomral reaction of mass be $N$ and force of friction acting upward be $f$. In equilibrium, vertical and horizontal forces should be balanced separately.
$$
f=M g
$$
(Given), $F=N$
As we know that, Force of friction $(f)=\mu N$
$$
=\mu F_{\ldots} \text { (iii) } \quad(\because F=N)
$$
From eqs. (i) and (iii), we have,
$$
\mu F=M g
$$
or $F=\frac{M g}{\mu}$
It is the minimum force to hold the block against the wall at rest.
Coefficient of friction between the block and the wall $=\mu$.
Let $F$ force be applied by finger on the block to hold the block against the wall. The nomral reaction of mass be $N$ and force of friction acting upward be $f$. In equilibrium, vertical and horizontal forces should be balanced separately.
$$
f=M g
$$
(Given), $F=N$
As we know that, Force of friction $(f)=\mu N$
$$
=\mu F_{\ldots} \text { (iii) } \quad(\because F=N)
$$
From eqs. (i) and (iii), we have,
$$
\mu F=M g
$$
or $F=\frac{M g}{\mu}$
It is the minimum force to hold the block against the wall at rest.
Looking for more such questions to practice?
Download the MARKS App - The ultimate prep app for IIT JEE & NEET with chapter-wise PYQs, revision notes, formula sheets, custom tests & much more.