I posted this question in the engineering section, but didn't get any replies there - hence posting it here. Below is a screen shot from state space analysis in "Control Engineering" by Ogata. http://www.flickr.com/photos/66943862@N06/6230432028/" [Broken] I am trying to get at Eqn 3-20 from Eqn 3-18. Can't the u part of the matrix also be written as [1/m 0]T instead of [0 1/m]T? What's the rationale in choosing one over the other?