Question

An iron chain lies on a rough horizontal table. It starts sliding when one-fourth of its length hangs over the edge of the table. The coefficient of static friction between the chain and surface of the table is.

• A. $\frac{1}{2}$
• B. $\frac{1}{3}$
• C. $\frac{1}{4}$
• D. $\frac{1}{5}$

Answer 1

Answer: (B)

$\frac{1}{3}$

Weight of hanging portion =$\frac{mg}{4}$
Weight of chain on table = $\frac{3mg}{4}$
Normal reaction R=$\frac{3mg}{4}$
Maximum friction = $\mu R=\frac{3\mu mg}{4}$
Equating the opposition frictional force with hanging portion of the chain that pulls.
$\frac{3\mu mg}{4}=\frac{mg}{4}$
$\mu =\frac{1}{3}$