Hootenanny said:
the derivative of acceleration is velocity. The derivative of velocity if displacement;
uhm, you got confused...
the time integral of acceleration is velocity, and the time integral of velocity is displacement...
the time derivative of displacement is velocity, and the time derivative of velocity is accelrration...
and in other words, the change rate in time of displacement at a certain time would be it's velocity on that specific time - this change rate is the slope of the x-t (displacent as Y an time as X) graph..
(and the change rate of velocity is acceleration - so the second derivative of displacement would give you acceleration)
and if you know the velocity at every moment summing it up over time (integrating it) would give you the total displacement.
you can see what derivative does if you look at it's definition:
to determine the slope of a line, you take it's Y value at point a -meaning f(a)
and at another point b -meaning f(b), you subtract f(b) from f(a) to get the height difference of the point and you divide this height difference by the distance between a and b.
now, derivative does the same, only it take two very close points and check the slope between them:
\frac{f(x)-f(x+\Delta x)}{\Delta x}
where \Delta x is very very small.
and this is how you get the tangential line's slope of a curve at point x...