Theory of Machine
The static balancing is satisfactory for low speed rotors but with increasing speeds, dynamic balancing becomes necessary. This is because, the

Unbalanced couples are caused only at higher speeds
Unbalanced forces are not dangerous at higher speeds
Effects of unbalances are proportional to the square of the speed
Effects of unbalances are directly proportional to the speed

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Theory of Machine
The frictional torque transmitted in a truncated conical pivot bearing, considering uniform pressure, is

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

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