nope, a true physics engine behaves the same time, always - if there are no outside forces. if you kick stuff around (use your mouse of fingers on touch devices) == outside force -> different outcome

this 2d world has no intrinsic random/chaotic forces (i.e. no wind) so everything behaves the same, always, forever. if you want your world to be more random you could write something like this (during the world initiation phase a.k.a. the first box2d-jquery call)

  $("h1, code, .box2d").box2d({'y-velocity':5, 'x-velocity':Math.random()}