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For a lightly damped vibrating system executing steady forced vibration, the phase lag of displacement, with respect to force at resonance is 

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ISRO VSSC Technical Assistant Mechanical 25 Feb 2018 Official Paper
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  1. 270°
  2. 90°
  3. 45°
  4. 0°

Answer (Detailed Solution Below)

Option 2 : 90°
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Detailed Solution

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Explanation:

At resonance (ω = ωn), phase angle ϕ is 90°.

When ω/ωn ≫ 1; the phase angle is very close to 180°. Here inertia force increases very rapidly and its magnitude is very large.

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