# Classical physics

Classical physics (or classical mechanics) is a group of physics theories that predate modern, more complete, and more widely applicable theories.

• Classical physics describes many aspects of nature at an everyday scale but neglects to explain things at very small (sub-atomic) and very large (cosmological) scales. It is a very successful theory, and many of its predictions have been experimentally verified.
• Classical physics studies the motion of macroscopic objects, from projectiles to parts of machinery and astronomical objects such as spacecraft to the movement of planets and stars.
• For objects governed by classical physics, if the present state is known, it is possible to predict how it will move in the future (determinism), and how it has moved in the past (reversibility).
• Classical physics has its roots in:
• Newton’s laws of motion, the law of conservation of energy, and the law of conservation of momentum are all fundamental laws of Newtonian mechanics. Newtonian mechanics is a branch of physics that describes the motion of objects under the influence of forces.
• Thermodynamics is a branch of physics that deals with the relationship between heat and work. Thermodynamics is based on the two laws of thermodynamics, which were developed in the 19th century by Carnot, Joule, and Kelvin.
• Maxwell’s electromagnetism is a branch of physics that describes the interaction of electric and magnetic fields. It is based on the four Maxwell equations, which were developed by James Clerk Maxwell in the 19th century.
• These three branches of physics are all related to each other. Newtonian mechanics can be used to describe the motion of objects in thermodynamic systems, and thermodynamics can be used to describe the energy changes that occur in electromagnetic systems.

Here are some examples of how these three branches of physics are related:

• The heat engine is a thermodynamic device that converts heat into work. The efficiency of a heat engine is limited by the laws of thermodynamics and the laws of Newtonian mechanics.
• The electric generator is an electromagnetic device that converts mechanical energy into electrical energy. The operation of an electric generator is based on the laws of electromagnetism and the laws of Newtonian mechanics.
• The light bulb is an electromagnetic device that converts electrical energy into light energy. The operation of a light bulb is based on the laws of electromagnetism and the laws of thermodynamics.
• Classical physics has some limitations. For example, classical physics cannot explain the behaviour of light at the atomic and subatomic levels. This is because light behaves both like a wave and a particle, which is something that classical physics cannot describe. These limitations are explored in the field of quantum mechanics (quantum physics).

Summary