Mechanics Classical Mechanics Mechanics Classical Mechanics Classical Physics

Mechanics: “Classical” Mechanics

Mechanics: “Classical” Mechanics • “Classical” Physics: “Classical” Before the 20 th Century The foundation of pure & applied macroscopic physics & engineering! – Newton’s Laws + Boltzmann’s Statistical Mechanics (& Thermodynamics): Describe most of macroscopic world! – However, at high speeds (v ~ c) we need Special Relativity: (Early 20 th Century: 1905) Ch. 14 of M&T – Also, for small sizes (atomic & smaller) we need Quantum Mechanics: (1900 through ~ 1930) Physics 4307! “Classical” Mechanics: (17 th & 18 th Centuries) Still useful today!

Mechanics • The science of HOW objects move (behave) under given forces. • (Usually) Does not deal with the sources of forces. Answers the question: “Given the forces, how do objects move”? • Forces are classified into four types: Four Fundamental Forces Of Nature! – Mechanics (in some form) applies to all four!

The 4 Fundamental Forces of Nature The Sources of these forces: In order of decreasing strength • Strong Nuclear Force: – Binds nuclei together. Still being researched. • Electromagnetic Force: – E&M phenomena. Chemical forces. Most everyday forces. Maxwell, Coulomb, Ampere, Faraday, . . . • Weak Nuclear Force: – Nuclear decay. Fermi, Bethe & others. Still being researched. • Gravitational Force: – Newton (“classical” mechanics) – Einstein (general relativity)

The 4 Fundamental Forces of Nature The Sources of these forces: In order of decreasing strength

The 4 Fundamental Forces of Nature “Electro-Weak” Force – Since ~ the late 1960’s, in some sense have reduced the 4 fundamental forces to 3! – The Electromagnetic Force & the Weak Nuclear Force were combined into one theory. – S. Weinberg & A. Salaam: The 1972 Nobel Prize in Physics!

The Standard Model of Particle Physics The “Periodic Table for Elementary Particles”! Quantum Chromodynamics (QCD) and the Electroweak Theory Protons & Neutrons consist of 3 Quarks each.

Standard Model

Standard Model

Standard Model

The Rest of Physics! • What we’ve mentioned is all of physics except: • Statistical Mechanics: (Physics 4302) – The mechanics of systems with huge numbers of particles (>> ~ 1023). – Uses probability & statistics methods to calculate the macroscopic properties of a system from the microscopic force laws between the particles. – The major LINK between microscopic & macroscopic physics! – Contains Thermodynamics as a sub-theory!