# A Coin Kept at a Distance of 5cm from the Centre of a Turntable of Radius 1.5m Just Begins to Slip When the Turntable Rotates at a Speed of 90 R.P.M. - Physics

A coin kept at a distance of 5cm from the centre of a turntable of radius 1.5m just begins to slip when the turntable rotates at a speed of 90 r.p.m. Calculate the coefficient of static friction between the coin and the turntable.

[g = 9.8 m/s2]

#### Solution

Given that r = 5 cm = 0.05 m,
n = 90 r.p.m. = 1.5 Hz
Limiting force of static friction = Centrifugal force

mu_smg=mromega^2

thereforemu_s=romega^2/g=r(2pin)^2/g

thereforemu_s=(4rpi^2n^2)/g

thereforemu_s=(4*0.05*(3.14)^2*(1.5)^2)/9.8

thereforemu=0.4527

Concept: Centrifugal Forces
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