Question

A coin place on a rotating turntable just slips of it is placed at distance of $4cm$ from the centre. If angular velocity of the turntable is doubled, it will just slip at a distance of

• A. $1cm$
• B. $2cm$
• C. $4cm$
• D. $8cm$

Answer 1

The correct option is A $1cm$

Let $w$ = angular velocity.
So,
$F=m{w}^{2}r$
$F_{slip}=m{w}^{2}4.-->eqn\left(1\right)$
Now if angular velocity is doubled-
$F_{slip}=m(2w{)}^2{R}_2$
$F_{slip}=4m{w}^2{R}_2-->eqn\left(2\right)$
solving 1 and 2-
$m{w}^{2}4=4m{w}^2{R}_2$
so,
$R_2=1cm$