Question

A block of mass $1$ kg is kept on the surface of a circular disc at a distance of $10$ cm from centre of disc, which is rotating in horizontal plane about it's own axis. The minimum coefficient of static friction between two surfaces in contact, so that block does not skid if angular velocity of disc is $\frac{150}{\pi }rpm$ $(Takeg=10m{s}^{-2})$:

• A. $0.2$
• B. $0.25$
• C. $0.4$
• D. $0.5$

Answer 1

Answer: (B)

$0.25$

By equating Torque, we get
$Fr=I\alpha$
$\left(\mu Mg\right)r=I\omega =\frac{M{r}^2\omega }{2}$

$\mu =\frac{r\omega }{2g}=\frac{0.1}{2\times 10}\times \frac{150\times 2\pi }{60\pi }$

$=0.25$