Which of the following is TRUE for vibration of a mechanical system
1
Damping ratio (ξ) is the ratio of the critical damping to the actual damping
2
The damping can be obtained from the response of the system under forced vibration using logarithmic decrement method
3
For damped mechanical systems, the amplitude of vibration tends to become infinity when excitation frequency (ω) reaches the system's natural frequency (ωn)
4
Amplitude ratio and transmissibility of a vibration isolator is unity when the frequency of exciting force is √2 times the natural frequency