The instantaneous velocity of an object can be negative. Even though the average velocity of the object in an entire trip is positive, the instantaneous velocity can be negative if the object is moving in negative direction. This direction depends upon the observer. If he considers direction away from him in the right as positive then the direction towards him in the left is negative.
Instantaneous
velocity in definition is the average velocity in given particular moment time.
Hence, it underlies the context of each velocity at each occupied time and
space at that particular moment where you are. Moreover, talking about velocity
is vector quantity, which means it both has magnitude and direction. Furthermore,
this positive and negative sign attributed to their number means only the
specific direction in which the object is going. For example in analogy to average
velocity, the initial position of the object at the moment is 2 m/s to the
right then the object suddenly changes his position to 3 m/s to the left as his
final position. Which is, the exact opposite of the former direction then
indicates that the final position is negative, contrary to the initial
direction. Just remember that the negative values connoted on the numbers can
indicate the opposite direction of either the initial position or an object is
downward.
