Theory of Machine
The example of rolling pair is

Bolt and nut
Ball and socket joint
Lead screw of a lathe
Ball bearing and roller bearing

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Theory of Machine
The frictional torque transmitted in a flat collar bearing, considering uniform pressure, is (where r₁ and r₂ = External and internal radii of collar respectively)

(2/3). μ W [(r₁³ - r₂³)/(r₁² - r₂²)]
(1/2). μ W (r₁ + r₂)
(1/2). μ W [(r₁³ - r₂³)/(r₁² - r₂²)]
(2/3). μ W (r₁ + r₂)

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