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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 

This question was previously asked in
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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