What is the difference between instantaneous speed and instantaneous velocity? The instantaneous velocity is the ratio of displacement and the time duration provided the time duration is very small (Infinitesimal with time duration approaching zero).
Instantaneous speed is the magnitude of instantaneous velocity and so can never be negative.
Instantaneous speed measures how fast a particle is moving; instantaneous velocity measures how fast and in what direction it’s moving.
As said above, Instantaneous speed is the magnitude of instantaneous velocity and so can never be negative. For example, a particle with instantaneous velocity Vx = 25 m/s and a second particle with Vx = -25 m/s are moving in the opposite direction at the same instantaneous speed 25 m/s.
Please note that Average speed is not the magnitude of average velocity. See the difference between average speed and average velocity.
Also Read: (suggested reading)
Difference between average speed and average velocity
Instantaneous Velocity – definition & equation with solved problem
Average velocity – definition, formula
Instantaneous Acceleration – definition & formula with solved problem
Average Acceleration and its formula & solved numerical problems