Greetings all, I apologize for joining your forum just to inquire about something that should be relatively simple, but you seem like a group of physics geeks able to articulate coherent arguments, and I need someone/s to help me see a different perspective on how to make an argument. For the record I'll state that I'm not exactly uneducated in this realm myself, but I'm far enough from day-to-day classical mechanics that I can make some pretty stupid mistakes, and am no-longer fluidly conversant in all of the relevant theorems/etc. I'm faced with an instructor who believes that an object at rest, is _not_ in uniform motion (bizarrely this seems an awfully common belief online!). "An object in uniform motion has a constant velocity - an object at rest has no velocity at all!"... I have tried the route of explaining that constant zero velocity is a constant velocity, I've tried the route of pointing out that any acceleration would cause V to vary from constant zero. These arguments are not leading to understanding, apparently because there's an embedded belief that zero velocity ("no motion") is somehow a privileged third state that is different from both "constant velocity" and "changing velocity" (a third category different from "uniform motion" and "non-uniform motion"). If only Newton hadn't phrased the first law in terms of "state of rest or uniform motion in a straight line"... At least online, everyone seems fixated on the "uniform motion in a straight line" as somehow being a completely different thing than "state of rest"... It seems that there /must/ be a theorem out there, or a proof, that says something like "an object in a state of uniform motion in one inertial reference frame, is in uniform motion in every inertial reference frame", or "an object moving at a constant velocity in one inertial reference frame, is moving at a constant velocity in every inertial reference frame" (or the similar for delta-V). Such a theorem would allow proof that (constant) zero velocity is just a specific case of constant velocity, and isn't somehow privileged. Without that, I'm not seeing any obvious way to combat the thinking that a thing with zero velocity somehow has an undefined "no velocity at all" velocity. Any suggestions?