Final answer:
The subject of the question is physics, focusing on mechanics and electromagnetism in the context of submarine propeller dynamics, forces between currents, and pressure on submerged hatches.
Step-by-step explanation:
The thrust developed by the submarine propeller is a concept related to physics, specifically concerning mechanics and electromagnetism. The various questions presented refer to angular motion and torque, water resistance's effect on rotational velocity, magnetic fields created by electric currents, and pressure differences in fluid statics. For instance, the problem regarding the nuclear submarine propeller's moment of inertia and rotation rate is a classical mechanics problem that involves the angular kinetic energy and water resistance.
Another question requiring calculation of the force between two current-carrying wires involves principles from electromagnetism, such as the magnetic force between parallel currents. Similarly, calculating the force needed to open a submarine hatch due to water pressure includes applying knowledge of fluid statics and pressure force calculations.