Question

Consider a single degree of freedom system with viscous damping excited by a harmonic force. At resonance, the phase angle(in degree) of the displacement with respect to the exciting force is

• A. 0
• B. 45
• C. 90
• D. 135

Answer 1

The correct option is C 90

Phase diagram for

$\frac{\omega }{{\omega }_n}=1$

$X:\text{Displacement}$
$F_0:\text{Excitation force}$
$c\omega X:\text{Damping force}$
$kX:\text{Spring force}$
$m{\omega }^{2}X:\text{Inertia force}$