Final answer:
General relativity is used in scenarios involving strong gravitational forces and large masses, while special relativity is used in situations with high speeds or near the speed of light. Quantum mechanics explains particle behavior at a subatomic level, and classical physics is applicable in everyday situations with lower speeds and weaker gravitational forces.
Step-by-step explanation:
General relativity is utilized in situations where strong gravitational forces and the behavior of objects in the presence of large masses need to be understood. It is applicable in scenarios such as the motion of celestial bodies, the bending of light around massive objects, and the study of black holes.
Special relativity is used when the relative motion of objects moving at high speeds or near the speed of light is being considered. It is relevant in areas like particle physics, atomic and nuclear physics, and the study of cosmic rays.
Quantum mechanics is employed to explain the behavior of particles at the subatomic level and their interaction with electromagnetic fields. It is used in fields such as quantum physics, atomic and molecular physics, and solid-state physics.
Classical physics, which includes Newtonian physics, is applicable in everyday situations where speeds are much lower than the speed of light and gravitational forces are not extremely strong. It can be used to analyze the motions of objects on Earth, the behavior of fluids, and concepts like energy conservation.