Another look at the describing equations of dynamics

We look at the fundamental equations of analytical dynamics from a different per-spective. We discuss an additional way of evaluating the approaches for deriving the equations of motion, and we show that all of the fundamental equations can be viewed as projections of the force and moment balances onto directions affected by the velocity variables. We re-classify the existing approaches into two parts: Those based on vector variational principles, and those based on scalar variational principles. We discuss the relative merits and disadvantages of these approaches.