What is defined as the science relating to the energy of gases in motion?

The science relating to the energy of gases in motion is known as aerodynamics. This field focuses specifically on the behavior of air as it interacts with solid objects, such as aircraft or vehicles. By studying aerodynamics, engineers and scientists can understand how air flows around objects, the forces acting upon them, and how to optimize designs for efficiency and performance.

Aerodynamics encompasses several key principles, including lift, drag, and turbulence, which are critical for flight and the design of vehicles that operate in the air. It plays a vital role in various applications, from improving the flight performance of airplanes to enhancing the fuel efficiency of cars.

The other options refer to related but distinct concepts. Aeronautics broadly covers the design and development of aircraft and spacecraft but does not specifically focus on the energy of gases. Aerospace mechanics involves the mechanical systems involved in the aviation and space sectors. Fluid dynamics, while closely related, is the broader study of the behavior of fluids (liquids and gases) in motion, and may include aspects beyond just gases, such as liquids.

Thus, aerodynamics is the precise field that addresses the kinetic energy and forces associated with gases in motion, making it the most accurate answer to the question.