Theory of Machine
In under damped vibrating system, if x₁ and x₂ are the successive values of the amplitude on the same side of the mean position, then the logarithmic decrement is equal to

loge(x₁/x₂)
log(x₁.x₂)
log(x₁/x₂)
x₁/x₂

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Theory of Machine
A rotor which is balanced statically but not dynamically is supported on two bearings L apart and at high speed of the rotor, reaction on the left bearing is R. The right side of the bearing is shifted to a new position 2L apart from the left bearing. At the same rotor speed, dynamic reaction on the left bearing in the new arrangement will

Become equal to 2R
Become equal to R/2
Become equal to R/4
Remain same as before

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