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Consider the following statements. Transmissibility of vibrations (1) Is more than 1, when ω/ωn < √2  (2) Is less than 1, when ω/ωn > √2  (3) Increases as the damping is increased

Consider the following statements. Transmissibility of vibrations (1) Is more than 1, when ω/ωn < √2  (2) Is less than 1, when ω/ωn > √2  (3) Increases as the damping is increased Correct Answer 1 and 2 only

Concept:

In the vibration isolation system, the ratio of the force transmitted to the force applied is known as the isolation factor or transmissibility ratio.

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  • When ω/ωn = 0 ⇒ TR = 1, (independent of ζ)
  • When ω/ωn = 1 and ξ = 0 ⇒ TR = ∞, (independent of ζ)
  • When frequency ratio ω/ωn = √2, then all the curves pass through the point TR = 1 for all values of damping factor ξ.
  • When frequency ratio ω/ωn < √2, then TR > 1 for all values of damping factor ξ. This means that the force transmitted to the foundation through elastic support is greater than the force applied.
  • When frequency ratio ω/ωn > √2, then TR < 1 for all values of damping factor ξ. This shows that the force transmitted through elastic support is less than the applied force. Thus vibration isolation is possible only in the range of ω/ωn > √2. Here the force transmitted to the foundation increases as the damping is increased.
  • If ω/ωn > √2 then transmissibility increases with an increase in damping if ω/ωn < √2 then transmissibility decreases with an increase in damping

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