So i have been told that the first derivative of a position function x(t) with respect to time gives me the instantaneous velocity, but i also encountered other material online which stated that the derivative of displacement with respect to time is also instantaneous velocity. Now this kind of confuses me, i see how the rate at which your position is changing gives velocity, but how can that be true for displacement as well if displacement itself is a change in position?

  • $\begingroup$ Perhaps velocity relative the base configuration or something? Was that the context for the other definition? In fluid dynamics one often talks about displacement relative some original placement at least. (Physics definitions are heavily context dependent in my experience. Almost nothing seems to mean the same thing in two different places) $\endgroup$ – Emil Feb 2 '17 at 5:09

Displacement and position are just two words for the same thing, at least in this context. Displacement is a change in position, but position (or "location" or "coordinates", etc.) is just a change in position relative to some arbitrarily defined origin.

As @Emil said in the comments, the words people use to define physical quantities can vary quite a bit from one source to another.

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