Legend

 l or d = distance t = time v = speed/ velocity Vav = average speed l = change in distance t = change in time

Velocity / Speed

Often we say, "the car is moving at 60 km/h" or "he's walking at 1 m/s"  these are speeds.  When we say, "the car is moving at 60 km/h due east"   this quantity becomes a vector instead of a scalar as mentioned before.  60 km/h due east has a specifically name, called "velocity".

Here, we will take a look at constant speed, average speed and instantaneous speed.

Average speed =

distance traveled
time elapsed
 The rocket travels a distance measured along its actual path through space.  After a time, t, having gone a distance, l, its average speed is Vav = l/t.

Constant speed:

distance = constant speed x time

 An object traveling at a constant speed covers equal distances in equal intervals of time.
Instantaneous speed:
The central notion here is that l will become infinitely small as t becomes infinitesimally small, and yet their ratio,
 , will approach a finite limiting value.   This limiting value
 approached by as t --> 0 (that is, as t gets
infinitesimally small) is called the instantaneous speed, v.  Mathematically that's written as:

 To find the instantaneous speed of the bee at point P, determine the average speed over a tiny interval straddling P.  Then shrink l until Vav remains constant at the instantaneous speed, v.
 Vector Kinematics Acceleration