A second order system has a transfer function given by $$\mathrm G\left(\mathrm s\right)\;=\;\frac{25}{\mathrm s^2\;+\;8\mathrm s\;+\;25}$$ .If the system, initially at rest is subjected to a unit step input at t = 0, the second peak in response will occur at

A unity feedback control system has the open loop transfer function $$G\left(s\right)\;=\;\frac{4\left(1\;+\;2s\right)}{s^2\left(s\;+\;2\right)}$$ .If the input to the system is a unit ramp, the steady-state error will be

The steady state error of a stable 'type 0' unity feedback system for a unit step function is

A critically damped, continuous-time, second order system, when sampled, will have ( in Z domain)