My calculus I professor was an engineer, and liked to bring up that equations for events in the real world usually aren't pretty (non-linear). With that in the back of my mind, I started my first physics course this semester and we are doing the basic one dimensional movement of a particle, position, velocity, acceleration, usually with a simple function of t. I began to mesh the two ideas while I should have been paying attention, and it dawned on me, that in the real world (i know nothing of if this applies to actual particles, I mean bodies like a car or animal) no rate is ever constant. For example, a car's velocity from a standstill to any speed is not going to be constant, it accelerates. It's rate of acceleration can't be constant either, and neither can it's rate of it's rate of acceleration, etc. So, is it safe to say that a hypothetical equation that exactly modeled the position of the car could not be an equation that could be brought to a constant through repeated differentiation? Just the thoughts of a first year physics major!