Mechanics is the field in physics that studies the motion of objects and the forces that cause or change this motion. Mechanics is one of the oldest and most fundamental branches of physics, dealing with the behavior of physical bodies under the influence of forces, and it provides a framework for understanding the movement of everything from tiny particles to large celestial bodies.

Mechanics is typically divided into three main subfields:

1. Classical Mechanics: This is the study of macroscopic objects moving at speeds much slower than the speed of light. Classical mechanics is based on principles laid out by Isaac Newton and others. It includes:
   • Kinematics: The description of motion (e.g., position, velocity, and acceleration) without considering the forces that cause it.
   • Dynamics: The study of forces and torques and how they affect motion.
   • Statistical Mechanics: A branch that uses statistics to study systems with many particles, providing a bridge between microscopic and macroscopic properties.
2. Quantum Mechanics: This branch describes the behavior of particles on very small scales, such as atoms and subatomic particles. Unlike classical mechanics, quantum mechanics involves probabilities and uncertainties, and it is governed by principles that differ significantly from those of classical physics.
3. Relativistic Mechanics: This field applies to objects moving at speeds close to the speed of light or in strong gravitational fields. It incorporates Einstein's theory of relativity and is essential for understanding the physics of high-energy particles and cosmological phenomena.

Mechanics as a whole is foundational to understanding motion and energy in physics and is essential in fields like engineering, astronomy, and many technological applications.