Final answer:
The subject is physics, focused on the high school level, where concepts like fluid dynamics, wave reflection, buoyancy, and Newton's third law are applied to understand the action and reaction between water and surfaces in a pool.
Step-by-step explanation:
The question seems to involve the principles of physics, particularly concerning fluid dynamics and Newton's laws of motion. When water hits the side of a pool and travels in the opposite direction, it is an illustration of Newton's third law, which states that for every action, there is an equal and opposite reaction. This ties into various topics such as reflection of waves, pressure exerted by fluids, and forces in equilibrium.
For instance, when a swimmer exerts force on the pool wall, they accelerate in the opposite direction due to the reaction force. Additionally, the concept of pressure exerted on all sides of the swimmer under water can be explained using buoyancy, with greater pressure from below creating a net upward force, balancing the weight of the swimmer.
When considering the motion of billiard balls hitting the water similarly results in the transfer of energy and momentum, leading to a wave that travels to the opposite end of the pool and reflects back. The fluids dynamic concept is further illustrated by the experiment suggested, wherein hitting water with different hand gestures affects the way water moves, thereby demonstrating the impact of force application and surface area.