Question

A coin placed on a rotating table just slips if it is placed at a distance $4r$ from the centre. If we double the angular velocity of the table, then the coin will just slip when it is away from the centre at a distance equal to

• A. $4r$
• B. $2r$
• C. $r$
• D. $r / 4$

Answer 1

Answer: (C)

$r$

Answer 2

$\therefore \omega =\sqrt{\frac{? g}{r}} \, \therefore \omega \propto \frac{1}{\sqrt{r}} \, \Rightarrow r \propto \frac{1}{\omega ^{2}}$ Since $\omega$ is double thus, $r'=\frac{4 r}{4}=r$