Question

A circular disc is made to rotate in a horizontal plane about its centre at the rate of $2rps$. The greatest distance of a coin placed on the disc from its centre so that it does not skid is ($\mu$ is coefficient of friction, $g=10m{s}^{-2}$):

• A. $\frac{2\mu }{6.3}cm$
• B. $6.3\mu cm$
• C. $\frac{\mu }{6.3}cm$
• D. $\frac{\mu g}{6.3}cm$

Answer 1

The correct option is B $6.3\mu cm$

$\therefore$ Max. friction $=\mu N=\mu Mg$
$\mu Mg$ gives the centripetal acceleration
$\mu Mg=M{\omega }^{2}d$
$\mu g={\omega }^{2}d$
$\omega =2rps=2\times 2\pi$
$d=\left(0.063\mu \right)metres$
$d=6.3\mu$ $cm$