Processing math: 100%

A coin placed on a disc rotates with speed of 3313rev/min provided that the coin is not more than 10cm from the axis. Calculate the coefficient of static friction between the coin and the disc.

Given,
Frequency of rotation (f)=3313rev/min=100360rev/sec=0.56rev/sec
Radius (r)=10cm=0.1m
Coefficient of static friction (μs)=?

When the coin just sustain on the disc, the frictional force is equal to the centripetal force,
i.e Fs=mV2r
or, μsR=mω2r          [∵ Fs=μR]

or, μs=mω2rmg=(2πf)2rg        [∵ R=mg]
or, μs=4π2(0.56)20.110=0.123

Coefficient of static friction (μs)=0.123

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