KCET 2021 Physics Solved Paper

When the coin placed on a rotating table is first about to slips, then till the time the coin rotates along with the table, necessary centripetal force for rotation will be provided by the frictional force,
i.e.,mrω2=µmg
where,
m= mass of the coin,
r= distance of the coin from the centre of the table,
ω= angular velocity,
µ= coefficient of friction
and g= acceleration due to gravity.
Since, m,µ and g remains constant, sorω2= constant
⇒ r∝

1

ω2

or

r2

r1

=(

ω1

ω2

)2
Given, ω2=2ω1,r1=4‌cm
⇒

r2

r1

=(

ω1

2ω1

)2
or r2=

r1

4

=

4

4

=1‌cm