Compare and contrast speed, velocity, and acceleration. Why do their differences matter?

Speed is a scalar quantity, that is, it is a number and indicates how fast (or slow) one travels at any given time.

Velocity is a vector quantity, this means that it has magnitude and direction, that is, how fast an object travels and its where its going (speed + the direction in which the object moves).

Acceleration is the ratio of the velocity change over the time interval in which this velocity change occurred. Acceleration as well as velocity is a vector quantity so it is made up of magnitude and direction.

The differences between these three quantities are important for the description of the movement. In the case of speed and velocity, its difference lies in the fact that velocity indicates the direction in which the movement is taking place (and speed is only a number), which in many physical phenomena the direction of movement is an important property. And the difference between acceleration and velocity is that acceleration instead of a velocity indicates a change in velocity (either in magnitude, direction or both), which tells us how fast a velocity will increase or decrease over time.

unable to answer the rest since your question is incomplete

e/c, where e is its total energy