When deriving the EOM for a single-DOF vibrating system, e.g. spring-mass-damper system, which of the following statements is/are dynamics analysis. , velocity correct. (i) Static equilibrium analysis must be performed prior to the (ii) The kinematic variables of the system, i.e. the displacement and acceleration, are defined in the same direction. energy approach (based on principle of conservation of energy) can be used for this (iii) Both Newton's 2nd law of motion and the purpose