Transcript Chapter 1
Chapter 1 Figures from Halliday, Resnick, Walker, “Fundamentals of Physics” 9th edition as noted. Additional slides from Thorton & Rex, Modern Physics, 3rd ed slides, prepared by Anthony Pitucco, Ph.D., Pima Community College Book website Other websites ~400 BC EVOLUTION Philosophy Natural Philosophy & Science (study of) ~1600 ~1634 ~1687 ~ 1834 ~1890 Natural Science (knowledge based) (first ‘scientists’ appear) Classical Physics Physics & Chemistry become separate fields Modern Physics (emergence of relativity & quantum theory) ~1930 MECHANICS CLASSICAL PHYSICS 1.1 ELECTRICITY AND MAGNETISM THERMODYNAMICS CONSERVATION LAWS Classical Physics CONSERVATION LAWS Energy, Linear Momentum, Angular Momentum, Charge • Mechanics – – – – – – Galilieo Newton Kepler Hook Kepler … • Electromagnetism – – – – – – – – – Coulomb Oersted Young Ampere Faraday Henry Maxwell Hertz … • Thermodynamics – – – – – – Thompson Carnot Joule Clausius Kelvin … Conservation Laws • Conservation of energy: – The total sum of energy (in all its forms) is conserved in all interactions. • Conservation of linear momentum: – In the absence of external forces, linear momentum is conserved in all interactions. • Conservation of angular momentum: – In the absence of external torque, angular momentum is conserved in all interactions. • Conservation of charge: – Electric charge is conserved in all interactions. Mechanics Three laws describing the relationship between mass and acceleration. Newton’s first law (law of inertia): An object in motion with a constant velocity will continue in motion unless acted upon by some net external force. Newton’s second law: Introduces force (F) as responsible for the the change in linear momentum (p): Newton’s third law (law of action and reaction): The force exerted by body 1 on body 2 is equal in magnitude and opposite in direction to the force that body 2 exerts on body 1. Electromagnetism • Gauss’s law (ΦE): (electric field) • Gauss’s law (ΦB): (magnetic field) • Faraday’s law: • Ampère’s law: Thermodynamics • First law: The change in the internal energy ΔU of a system is equal to the heat Q added to a system plus the work W done by the system ΔU = Q + W • Second law: It is not possible to convert heat completely into work without some other change taking place. • The “zeroth” law: Two systems in thermal equilibrium with a third system are in thermal equilibrium with each other. • Third law: It is not possible to achieve an absolute zero temperature STUPID THINGS PEOPLE SAY • Lord Kelvin 1900 – “There is nothing new to be discovered in physics now. All that remains is more and more precise measurement.” • Albert Michelson 1894 – “The more important fundamental laws and facts of physical science have all been discovered, and these are so firmly established that the possibility of their ever being supplanted in consequence of new discoverys is exceedingly remote…” Some Mysteries of 1895-1915 • What are the positive and negative charges in a material and how are they arranged? (atom) JDalton’s 1808 Chemical Philosophy sketches http://en.wikipedia.org/wiki/File:Daltons_symbols.gif • How does one explain the distribution of velocities in a gas? (Maxwell-Boltzmann) Some Mysteries of 1895-1915 • Why do electrons moving through a gas loose energy in increments? (Franck-Hertz) Wikipedia on Franck-Hertz • Why do ‘alpha rays’ bounce back 180o? (GeigerMarsden-Rutherford) • What medium do light waves travel in? (MichelsonMorley) Some Mysteries of ~1895 • Why does light kick electrons out of a surface only above a certain frequency which is different for each material? (photoelectric effect) • What is this radioactivity stuff? Some Mysteries of ~1895 • How does one explain the perihelion precession of planet Mercury? Wikipedia on precession of Mercury • Why does the electron have a magnetic moment? (Stern-Gerlach) • Is light a particle or a wave? ~400 BC EVOLUTION Philosophy Natural Philosophy & Science (study of) ~1600 ~1634 ~1687 ~ 1834 ~1890 Natural Science (knowledge based) (first ‘scientists’ appear) Classical Physics Physics & Chemistry become separate fields Modern Physics (emergence of relativity & quantum theory) ~1930 PEOPLE OF MODERN PHYSICS 10 minute presentations *** next week *** Historical Characters • • • • • • • • • William Hamilton (1805-1865) David Hilbert (1862-1943) Max Planck (1858-1947) Albert Einstein (1879-1955) Niels Bohr (1885-1962) Werner Heisenberg (1901-1976) Samuel Goudsmit (1902-1978) George Uhlenbeck (1900-1988) Hendrik Lorentz (1853-1928) • • • • • • • • • • Louis de Broglie (1892-1987) Erwin Schrödinger (1887-1961) Max Born (1882-1970) Wolfgang Pauli (1900-1958) Paul Dirac (1902-1984) John von Neumann (1903-1957) Otto Stern (1888-1969) Walther Gerlach (1889-1979) Pieter Zeeman (1865-1943) Paul Ehrenfest (1880-1933) Women People • • • • • • • • • • • • • • • Lise Meitner 1878-1968 – Radioactivity & nuclear Gertrude Scharff Goldhaber 1911-1998 – neutrons emitted during fission Sulamith Goldhaber 1923-1965 – Kaon studies, CP violation, Time-reversal violation Noeme Benczer Koller – 2 photon transitions, Administrative structure of physics in the US Bice Sechi-Zorn – Gluon jets Katherine Way 1903-1996 – Nuclear structure databases Chien-Shiung Wu 1912-1997 – Parity violation Evans Hayward Faye Ajzenberg-Selove E. Margaret Burbidge – B2FH Maria Goeppert-Mayer 1906-1912 – Nuclear shell model, spin-orbit, 235U Helen Quinn 1943– Unification of strong, weak, EM forces Rosalind Franklin 1920-1958 – X-ray crystallography of double helix Hertha Sponer 1895-1968 – Application of QM to atomic & molecular d Men People • • • • • • • • • • • • • • • Otto Hahn 1878-1968 Isidov Isaac Rabi 1898-1988 – Magnetic properties of nuclei Edward Teller 1908-2003 – “If you’ve got a problem, he’s got a bomb” Leo Szilard 1898-1964 – Conceived chain reaction, “scientist with a conscience” David Bohm 1917-1992 – McCarthyism, thesis work got classified before he could get a degree. Freeman Dyson 1923– Triga, JASON, “A-bomb kid” Eugene Wigner 1902-1995 – Symmetry groups Richard Feynman 1918-1988 – “½ genius - ½ buffoon, NO, all genius - all buffoon” Abdus Salam 1926-1996 – Elementary particles, electroweak theory Alvin Weinberg 1915-2006 – “When piles go critical in Chicago, we celebrate with wine, when piles go critical in Tennesse, we celebrate with Jack Daniels” Murray Gell-Mann 1929– “the man with 5 brains” Eugen Merzbacher 1921– Father sold radioactive toothpaste Larry Biedenharn 1922-1996 – Father 1st to sell Coca-cola Enrico Fermi 1901-1954 – “Sound of Music” c Pairs of characters • Joe Weber (1919-2000) / Virginia Trimble (1942-) – Did early maser work; considered the optical maser – quantum electronics, gravity wave, gravitation,…NAVAL ACADEMY GRAD, quantum electronics, gravity wave, gravitation,… • • • • • • • • • • Maurice (1911- ) / Gertrude Scharff Goldhaber Paul Dirac (1902 ) / Margit Wigner Margaret Burbidge (1919- ) / Geoffrey Burbidge (1925- ) D D D D D D d Presentation Evaluation About Who? Length of Presentation <8 min ~ 10 min >12 min Not Much Ave A Lot Presentation Style rough ave real smooth Talk was prepared last minute neutral far in advance Balance of Personal vs Physics Information all physics reasonable balance all personal Interesting facets of personal info uncovered had no life Ave movie star Photographs & artifacts of their life uncovered what’s a photograph? Ave YouTuber This person would be classified as a storm drain brick in the wall party animal no neutral yes Amount of Research Performed I wish I had picked this person to talk about x r y z t t stationary coordinate Position system (x,y,z,t) Forces & Acceleration Three astronauts, propelled by jet packs, push and guide a 120 kg asteroid toward a processing dock, exerting forces F1 = 32 N F2 = 55 N F3 = 41 N q1 = 30o q2 = 60o What is the asteroid’s acceleration? On Aug 10, 1972, a large meteor skipped across the atmosphere above western US and western Canada, much like a stone skipped across water. Kinetic Energy The meteorite’s mass was about 4 * 106 kg; it’s speed was about 15 km/s. Had it entered the atmosphere vertically; it would have hit the Earth with about the same speed. (a) Calculate the meteorite’s kinetic energy. (b) Express this in terms is tons of TNT. 1 ton TNT = 4.2*1015 J. Photograph by James M Baker http://ngm.nationalgeographic.com/2008/08/earth-scars/stone-text http://ngm.nationalgeographic.com/2008/08/earth-scars/alvarez-photography http://www.youtube.com/watch?v=ZUyoDkp30-U Conservation of Energy Conservation of Energy (reading graphs) Conservation of Energy (reading graphs) Conservation of Energy (reading graphs) Conservation of Energy (reading graphs) Conservation of Energy (reading graphs) Conservation of Momentum HRW 9-117 A collision occurs between a 2 kg particle traveling with velocity v1 4iˆ 5 ˆj m / s and a 4 kg particle traveling with velocity v2 6iˆ 2 ˆj m / s After the collision, the particles stick together. What is the final velocity? Conservation of Momentum Particle 1 Alpha particle m1 = 4 amu Particle 2 Oxygen nucleus m2 = 16 amu v2 f 1.20105 m / s q1 64o q2 51o Find v1i and v1f Conservation of Angular Momentum HRW 11-45 A man stands on a platform which is rotating at 1.2 rev/s. His arms are outstretched and he holds a brick in each hand. The total rotational inertia is 6 kg m2 . He brings his arms in so that the rotational inertia decreases to 2 kg m2 . What is his final rotational speed? Conservation of Angular Momentum HRW 11-46 The rotational inertia of a collapsing spinning star drops to 1/3 its initial value. What is the ratio of the new rotational kinetic energy to the initial rotational kinetic energy?