This is a good question. First, one lifecycle clearly does not fit all. Teams find themselves in a unique situation: team members are unique individuals with their own skills and preferences for working, let alone the scaling/tailoring factors such as team size, geographic distribution, domain complexity, organizational culture, and so on which vary by team. Because teams find themselves in a wide variety of situations shouldn’t a framework such as DA support several lifecycles? Furthermore, just from the raging debates on various agile discussion forums, in agile user groups, at agile conferences, and even within organizations themselves it’s very easy to empirically observe that agile teams are in fact following different types of lifecycles.
Of the two, lateral dynamics has proven to be the more complicated, requiring three-dimensional , multibody dynamic analysis with at least two generalized coordinates to analyze. At a minimum, two coupled, second-order differential equations are required to capture the principal motions.  Exact solutions are not possible, and numerical methods must be used instead.  Competing theories of how bikes balance can still be found in print and online. On the other hand, as shown in later sections, much longitudinal dynamic analysis can be accomplished simply with planar kinetics and just one coordinate.