Question

A coin is placed at the edge of a horizontal disc rotating about a vertical axis through its axis through speed $2rad{s}^{-1}$. The radius of the disc is 50 cm. Find the minimum coefficient of friction between disc and coin so that the coin does not slip (g=10$m{s}^{-2}$).

• A. 0.1
• B. 0.2
• C. 0.3
• D. 0.4

Answer 1

The correct option is B 0.2

Friction $f=mr{\omega }^2=\mu mg\Rightarrow \frac{50}{100}\times 4=\mu .10\Rightarrow \mu =0.2$

The coin does not slip if centripetal force necessary for rotation is provided by friction