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Mechanics

From Tilcayo Cats, the lean encyclopaedia by Tilcayo Knowledge Systems

Mechanics is the branch of physics devoted to the study of the motion of material objects.[1] One university course puts its two basic questions simply: how does an object move, and what does that motion depend on? The answers make up the two main parts of the subject, called kinematics and dynamics.[2]

Kinematics and dynamics

Kinematics is the study of motion without considering its causes.[3] It describes the way objects move, such as their velocity and their acceleration.[4] It does not take into account what the objects are made of.[5] In kinematics, the aim is to find a mathematical description of the motion being observed.[6]

Dynamics considers the forces that affect the motion of moving objects and systems. Newton's laws of motion are the foundation of dynamics.[7] These laws apply in the same way to situations on Earth and in space.[8] Some courses add a third part, energetics, which connects mechanics with other branches of science.[9]

Classical mechanics

Main article: Classical mechanics

Classical mechanics deals with the motion of anything, roughly speaking, that is larger than an atom or a molecule.[10] Its methods and ideas are at the foundation of any branch of science or engineering that is concerned with motion, from a star to an amoeba.[11] Newton's laws give a good approximation to motion only when objects move at speeds much less than the speed of light and are larger than most molecules; these limits define the realm of classical mechanics.[12][13]

The ideas of Isaac Newton were taken up by researchers after him. During the second half of the eighteenth century, much of the promise of Newton's Principia was realised, and what is now called "Newtonian mechanics" emerged in this process.[14] By the 1790s Newton's theory of gravity had become established among people researching orbital mechanics.[15]

Beyond classical mechanics

At the beginning of the 20th century, Albert Einstein developed the theory of relativity, and he and many other scientists developed quantum theory.[16] Relativity must be used when an object travels at more than about 1% of the speed of light, or is in a strong gravitational field such as the one near the Sun.[17] Quantum mechanics must be used for objects smaller than can be seen with a microscope.[18] Some ideas from classical mechanics, such as momentum, energy and angular momentum, carry over into quantum mechanics as well.[19]

Quantum mechanics is very successful at predicting the behaviour of tiny particles.[20] However, there is very little agreement, among physicists and among philosophers, about what the world is like according to quantum mechanics.[21]

References

  1. ↑ "Introduction". Mechanics course, ETSEIB, Universitat Politècnica de Catalunya. Retrieved 2026-10-18. Mechanics is the branch of physics devoted to the study of the motion of material objects.
  2. ↑ "Introduction". Mechanics course, ETSEIB, Universitat Politècnica de Catalunya. Retrieved 2026-10-18. these questions can be reduced to two fundamental ones: How is that motion? What does the motion depend on? The answers to those questions are the two main chapters in this subject: kinematics and dynamics, respectively.
  3. ↑ "Introduction to One-Dimensional Kinematics". OpenStax, College Physics 2e. Retrieved 2026-10-18. kinematics which is defined as the study of motion without considering its causes
  4. ↑ "Introduction to Dynamics: Newton's Laws of Motion". OpenStax, College Physics 2e. Retrieved 2026-10-18. The study of motion is kinematics, but kinematics only describes the way objects move—their velocity and their acceleration.
  5. ↑ "Introduction". Mechanics course, ETSEIB, Universitat Politècnica de Catalunya. Retrieved 2026-10-18. Kinematics describes the motion of the objects without taking into account their material characteristics.
  6. ↑ "Introduction". Mechanics course, ETSEIB, Universitat Politècnica de Catalunya. Retrieved 2026-10-18. In kinematics, we look for the mathematical expression of the different features of the motion under observation.
  7. ↑ "Introduction to Dynamics: Newton's Laws of Motion". OpenStax, College Physics 2e. Retrieved 2026-10-18. Dynamics considers the forces that affect the motion of moving objects and systems. Newton's laws of motion are the foundation of dynamics.
  8. ↑ "Introduction to Dynamics: Newton's Laws of Motion". OpenStax, College Physics 2e. Retrieved 2026-10-18. They are also universal laws in that they apply to similar situations on Earth as well as in space.
  9. ↑ "Introduction". Mechanics course, ETSEIB, Universitat Politècnica de Catalunya. Retrieved 2026-10-18. In order to connect Newtonian mechanics to other branches in science, this course includes a third chapter: energetics.
  10. ↑ "1.1: Introduction (University Physics I – Classical Mechanics, Gea-Banacloche)". LibreTexts. Retrieved 2026-10-18. Classical mechanics is the branch of physics that deals with the study of the motion of anything (roughly speaking) larger than an atom or a molecule.
  11. ↑ "1.1: Introduction (University Physics I – Classical Mechanics, Gea-Banacloche)". LibreTexts. Retrieved 2026-10-18. the methods and concepts of classical mechanics are at the foundation of any branch of science or engineering that is concerned with the motion of anything from a star to an amoeba
  12. ↑ "Introduction to Dynamics: Newton's Laws of Motion". OpenStax, College Physics 2e. Retrieved 2026-10-18. Newton's laws of motion produce a good approximation to motion only when the objects are moving at speeds much, much less than the speed of light and when those objects are larger than the size of most molecules
  13. ↑ "Introduction to Dynamics: Newton's Laws of Motion". OpenStax, College Physics 2e. Retrieved 2026-10-18. These constraints define the realm of classical mechanics
  14. ↑ "Newton's Philosophiae Naturalis Principia Mathematica". Stanford Encyclopedia of Philosophy. Retrieved 2026-10-18. During the second half of the eighteenth century the promise of the Principia was not only universally recognized by those active in empirical research, but a large fraction of this promise was realized. What we now call "Newtonian mechanics" emerged in this process
  15. ↑ "Newton's Philosophiae Naturalis Principia Mathematica". Stanford Encyclopedia of Philosophy. Retrieved 2026-10-18. By the 1790s Newton's theory of gravity had become established among those engaged in research in orbital mechanics
  16. ↑ "Introduction to Dynamics: Newton's Laws of Motion". OpenStax, College Physics 2e. Retrieved 2026-10-18. At the beginning of the 20 th century, Albert Einstein (1879–1955) developed the theory of relativity and, along with many other scientists, developed quantum theory.
  17. ↑ "1.1 Physics: An Introduction". OpenStax, College Physics 2e. Retrieved 2026-10-18. Relativity must be used whenever an object is traveling at greater than about 1% of the speed of light or experiences a strong gravitational field such as that near the Sun.
  18. ↑ "1.1 Physics: An Introduction". OpenStax, College Physics 2e. Retrieved 2026-10-18. Quantum mechanics must be used for objects smaller than can be seen with a microscope.
  19. ↑ "1.1: Introduction (University Physics I – Classical Mechanics, Gea-Banacloche)". LibreTexts. Retrieved 2026-10-18. momentum, energy, and angular momentum, carry over into quantum mechanics as well
  20. ↑ "Quantum Mechanics". Stanford Encyclopedia of Philosophy. Retrieved 2026-10-18. a mathematical machine for predicting the behaviors of microscopic particles — or, at least, of the measuring instruments we use to explore those behaviors — and in that capacity, it is spectacularly successful
  21. ↑ "Quantum Mechanics". Stanford Encyclopedia of Philosophy. Retrieved 2026-10-18. there is very little agreement, among physicists and among philosophers, about what the world is like according to quantum mechanics.
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