Final answer:
The study of masses in motion is known as kinetics, part of dynamics, which is about analyzing motion and its causes. Two bodies can exert forces on each other without physical contact, like through gravitational pull. Classical physics handles large, non-relativistic bodies, while general relativity is for high-speed objects or strong gravitational fields.
Step-by-step explanation:
The study of masses in motion is called kinetics, which is option b. Kinetics, as a part of dynamics in physics, focuses on analyzing the motion of objects and is mainly interested in understanding the causes of motion. It's vital to understand that dynamics itself has two branches: kinematics, which describes the motion without reference to its causes, and kinetics, which deals with forces and their effects on motion.
Answering the second question, two bodies do not have to be in physical contact to exert a force upon one another. This is evident in the phenomenon where objects are influenced by gravity, magnetic fields, and electrostatic forces at a distance.
In reviewing the available information, it becomes clear that kinematics is erroneously defined as the study of motion in option a, whereas the correct definition should only refer to describing the motion without considering the causes, which aligns with the provided definition for dynamics in option c.
Additionally, regarding the subfield of physics that describes small objects at high speeds or in strong gravitational fields, the general theory of relativity would be most appropriate. Classical physics, although capable of accurately studying the motion of large, non-relativistic bodies like a plane flying through the sky, is not well-suited for such extreme conditions.