Physics Two Dimensional Motion Question 104

Question: A coin, placed on a rotating turn-table slips, when it is placed at a distance of 9 cm from the centre.If the angular velocity of the turn-table is trippled, it will just slip, if its distance from the centre is

[CPMT 2001]

Options:

A) 27 cm B)9 cm C) 3 cm D) 1 cm

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Answer:

Correct Answer: D

Solution:

In the given condition friction provides the required centripetal force and that is constant. i.e. mw2r=constant

Therefore $ r\propto \frac{1}{{{\omega }^{2}}} $ \ $ r _{2}=r _{1}{{( \frac{{\omega _{1}}}{{\omega _{2}}} )}^{2}}=9{{( \frac{1}{3} )}^{2}}=1,cm $