The study of variation in velocity falls under the domain of kinematics, a branch of physics that deals with the motion of objects without considering the forces that cause that motion.

Here are some of the specific areas within kinematics where the variation of velocity is studied:

* Acceleration: This is the rate at which velocity changes over time. It's a fundamental concept in kinematics and is directly related to the variation of velocity.

* Jerk: This is the rate at which acceleration changes over time. It's a measure of how smoothly or abruptly velocity changes.

* Motion graphs: Graphs like velocity-time graphs and acceleration-time graphs are used to visualize and analyze how velocity changes over time.

* Equations of motion: These are mathematical equations that describe the relationship between displacement, velocity, acceleration, and time. They can be used to predict how velocity will change under different conditions.

While physicists study variation in velocity, other disciplines may also be interested in this concept depending on their field of study. For example:

* Engineers use the principles of kinematics to design and analyze systems involving moving parts.

* Astronomers study the variation of velocity of celestial objects to understand their motion and evolution.

* Biomechanics professionals study the variation in velocity of body parts to understand human movement and improve performance.

Ultimately, anyone who studies the motion of objects will be interested in understanding how velocity changes over time.