Question

A coin is placed on a rotating turn table slips if it is placed at a minimum distance of 9cm from the centre. If the angular velocity of the turn table is tripled, it wilt just slip if the distance from the centre is:

• A. 9 cm
• B. 3 cm
• C. 1.5 cm
• D. 1 cm

Answer 1

Answer: (D)

Centripetal force on coin placed on a rotating table is $=mr{\omega }^2$ In both case the force required is same. Hence, $m{r}_1{\omega }_1^2=m{r}_2{\omega }_2^2$ Given: $r_1=9cm$ ${\omega }_2=3{\omega }_1$ $9\times {\omega }_1^2,=r_2{(3{\omega }_1)}^2$ $9{\omega }_1^2=r_{2}9{\omega }_1^2$ $r_2=\frac{9}{9}=1cm$