Newtonian mechanics, formulated by Sir Isaac Newton, provides a powerful framework for understanding the motion of objects under the influence of forces. However, there are certain situations and scales where Newtonian mechanics is not applicable or becomes insufficient to explain the observed phenomena. Here are a few examples:
Quantum Mechanics: Newtonian mechanics fails to accurately describe the behavior of particles at the quantum level. Quantum mechanics, a branch of physics, is required to explain the behavior of subatomic particles, such as electrons and photons. Quantum mechanics introduces probabilistic descriptions, wave-particle duality, and uncertainty principles, which are fundamentally different from the deterministic nature of Newtonian mechanics.
Relativistic Regime: At extremely high speeds close to the speed of light or in the presence of strong gravitational fields, Newtonian mechanics breaks down, and the theory of general relativity becomes necessary. General relativity provides a more accurate description of gravity and spacetime curvature in these extreme conditions.
Microscopic and Molecular Scale: When dealing with systems involving individual molecules, atoms, or smaller entities, Newtonian mechanics becomes less applicable. Phenomena such as Brownian motion, thermal fluctuations, and quantum effects dominate the behavior at these scales. Statistical mechanics and quantum mechanics are more appropriate for describing such systems.
High-Energy Physics: In the study of particle physics at extremely high energies, such as those reached in particle accelerators like the Large Hadron Collider (LHC), Newtonian mechanics is inadequate. Particle interactions at these energies involve processes that require quantum field theory and the Standard Model of particle physics for accurate descriptions.
Strongly Interacting Systems: In systems with strong interactions between constituents, such as fluids with turbulent flow, complex materials, or systems undergoing phase transitions, the simplified assumptions of Newtonian mechanics may not be sufficient. More advanced theories and computational methods, like fluid dynamics, statistical mechanics, or condensed matter physics, are employed to understand and model such systems.
It's important to note that Newtonian mechanics is still highly accurate and widely applicable for a wide range of everyday phenomena and engineering applications, such as classical mechanics, celestial mechanics, and most macroscopic systems. However, in the domains mentioned above, more advanced theories are needed to provide accurate descriptions and predictions.