Question

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]

Answer 1

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`