Question

A metallic chain $1m$ long lies on a horizontal surface of a table. The chain starts sliding on the table if $25cm$ (or more of it) hangs over the edge of a table. The correct value of the coefficient of friction between the table and the chain is

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

Answer 1

The correct option is A $\frac{1}{3}$

Let the mass of the chain be $m.$

The chain just begins to slide means that the force of gravity becomes equal to the force of friction.

When $0.25metres$ hangs, the gravity force is $0.25mg$

Since $0.75metres$ is on the table, the force of friction is $0.75\mu mg.$

The chain starts to slide means, both the forces have become equal.

$\mu \times 0.75mg=0.25mg$

$\mu =\frac{0.75}{0.25}=\frac{1}{3}$