Reply to Brews ohare   Brews I am fully aware of the difference between kinematics and kinetics This aticle doesnt need to involve that difference  You quoted above an expression for acceleration That expression is correct I am not disagreeing with it But it tells us absolutely nothing that would enable us to solve a motion problem  To solve a problem in motion we need an input force If it only kinematics we still need an input acceleration  We always need some kinds of contraints or known accelerations before we can determine a trajectory  The solution to your general acceleration equation above is Anything