Natural Units and the Scales of Fundamental Physics C R
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Metric System Units of Length
Math 0300 METRIC SYSTEM UNITS OF LENGTH Þ To convert units of length in the metric system of measurement The basic unit of length in the metric system is the meter. All units of length in the metric system are derived from the meter. The prefix “centi-“means one hundredth. 1 centimeter=1 one-hundredth of a meter kilo- = 1000 1 kilometer (km) = 1000 meters (m) hecto- = 100 1 hectometer (hm) = 100 m deca- = 10 1 decameter (dam) = 10 m 1 meter (m) = 1 m deci- = 0.1 1 decimeter (dm) = 0.1 m centi- = 0.01 1 centimeter (cm) = 0.01 m milli- = 0.001 1 millimeter (mm) = 0.001 m Conversion between units of length in the metric system involves moving the decimal point to the right or to the left. Listing the units in order from largest to smallest will indicate how many places to move the decimal point and in which direction. Example 1: To convert 4200 cm to meters, write the units in order from largest to smallest. km hm dam m dm cm mm Converting cm to m requires moving 4 2 . 0 0 2 positions to the left. Move the decimal point the same number of places and in the same direction (to the left). So 4200 cm = 42.00 m A metric measurement involving two units is customarily written in terms of one unit. Convert the smaller unit to the larger unit and then add. Example 2: To convert 8 km 32 m to kilometers First convert 32 m to kilometers. km hm dam m dm cm mm Converting m to km requires moving 0 . -
An Atomic Physics Perspective on the New Kilogram Defined by Planck's Constant
An atomic physics perspective on the new kilogram defined by Planck’s constant (Wolfgang Ketterle and Alan O. Jamison, MIT) (Manuscript submitted to Physics Today) On May 20, the kilogram will no longer be defined by the artefact in Paris, but through the definition1 of Planck’s constant h=6.626 070 15*10-34 kg m2/s. This is the result of advances in metrology: The best two measurements of h, the Watt balance and the silicon spheres, have now reached an accuracy similar to the mass drift of the ur-kilogram in Paris over 130 years. At this point, the General Conference on Weights and Measures decided to use the precisely measured numerical value of h as the definition of h, which then defines the unit of the kilogram. But how can we now explain in simple terms what exactly one kilogram is? How do fixed numerical values of h, the speed of light c and the Cs hyperfine frequency νCs define the kilogram? In this article we give a simple conceptual picture of the new kilogram and relate it to the practical realizations of the kilogram. A similar change occurred in 1983 for the definition of the meter when the speed of light was defined to be 299 792 458 m/s. Since the second was the time required for 9 192 631 770 oscillations of hyperfine radiation from a cesium atom, defining the speed of light defined the meter as the distance travelled by light in 1/9192631770 of a second, or equivalently, as 9192631770/299792458 times the wavelength of the cesium hyperfine radiation. -
Lesson 1: Length English Vs
Lesson 1: Length English vs. Metric Units Which is longer? A. 1 mile or 1 kilometer B. 1 yard or 1 meter C. 1 inch or 1 centimeter English vs. Metric Units Which is longer? A. 1 mile or 1 kilometer 1 mile B. 1 yard or 1 meter C. 1 inch or 1 centimeter 1.6 kilometers English vs. Metric Units Which is longer? A. 1 mile or 1 kilometer 1 mile B. 1 yard or 1 meter C. 1 inch or 1 centimeter 1.6 kilometers 1 yard = 0.9444 meters English vs. Metric Units Which is longer? A. 1 mile or 1 kilometer 1 mile B. 1 yard or 1 meter C. 1 inch or 1 centimeter 1.6 kilometers 1 inch = 2.54 centimeters 1 yard = 0.9444 meters Metric Units The basic unit of length in the metric system in the meter and is represented by a lowercase m. Standard: The distance traveled by light in absolute vacuum in 1∕299,792,458 of a second. Metric Units 1 Kilometer (km) = 1000 meters 1 Meter = 100 Centimeters (cm) 1 Meter = 1000 Millimeters (mm) Which is larger? A. 1 meter or 105 centimeters C. 12 centimeters or 102 millimeters B. 4 kilometers or 4400 meters D. 1200 millimeters or 1 meter Measuring Length How many millimeters are in 1 centimeter? 1 centimeter = 10 millimeters What is the length of the line in centimeters? _______cm What is the length of the line in millimeters? _______mm What is the length of the line to the nearest centimeter? ________cm HINT: Round to the nearest centimeter – no decimals. -
Modern Physics Unit 15: Nuclear Structure and Decay Lecture 15.1: Nuclear Characteristics
Modern Physics Unit 15: Nuclear Structure and Decay Lecture 15.1: Nuclear Characteristics Ron Reifenberger Professor of Physics Purdue University 1 Nucleons - the basic building blocks of the nucleus Also written as: 7 3 Li ~10-15 m Examples: A X=Chemical Element Z X Z = number of protons = atomic number 12 A = atomic mass number = Z+N 6 C N= A-Z = number of neutrons 35 17 Cl 2 What is the size of a nucleus? Three possibilities • Range of nuclear force? • Mass radius? • Charge radius? It turns out that for nuclear matter Nuclear force radius ≈ mass radius ≈ charge radius defines nuclear force range defines nuclear surface 3 Nuclear Charge Density The size of the lighter nuclei can be approximated by modeling the nuclear charge density ρ (C/m3): t ≈ 4.4a; a=0.54 fm 90% 10% Usually infer the best values for ρo, R and a for a given nucleus from scattering experiments 4 Nuclear mass density Scattering experiments indicate the nucleus is roughly spherical with a radius given by 1 3 −15 R = RRooA ; =1.07 × 10meters= 1.07 fm = 1.07 fermis A=atomic mass number What is the nuclear mass density of the most common isotope of iron? 56 26 Fe⇒= A56; Z = 26, N = 30 m Am⋅⋅3 Am 33A ⋅ m m ρ = nuc p= p= pp = o 1 33 VR4 3 3 3 44ππA R nuc π R 4(π RAo ) o o 3 3×× 1.66 10−27 kg = 3.2× 1017kg / m 3 4×× 3.14 (1.07 × 10−15m ) 3 The mass density is constant, independent of A! 5 Nuclear mass density for 27Al, 97Mo, 238U (from scattering experiments) (kg/m3) ρo heavy mass nucleus light mass nucleus middle mass nucleus 6 Typical Densities Material Density Helium 0.18 kg/m3 Air (dry) 1.2 kg/m3 Styrofoam ~100 kg/m3 Water 1000 kg/m3 Iron 7870 kg/m3 Lead 11,340 kg/m3 17 3 Nuclear Matter ~10 kg/m 7 Isotopes - same chemical element but different mass (J.J. -
Dimensional Analysis and the Theory of Natural Units
LIBRARY TECHNICAL REPORT SECTION SCHOOL NAVAL POSTGRADUATE MONTEREY, CALIFORNIA 93940 NPS-57Gn71101A NAVAL POSTGRADUATE SCHOOL Monterey, California DIMENSIONAL ANALYSIS AND THE THEORY OF NATURAL UNITS "by T. H. Gawain, D.Sc. October 1971 lllp FEDDOCS public This document has been approved for D 208.14/2:NPS-57GN71101A unlimited release and sale; i^ distribution is NAVAL POSTGRADUATE SCHOOL Monterey, California Rear Admiral A. S. Goodfellow, Jr., USN M. U. Clauser Superintendent Provost ABSTRACT: This monograph has been prepared as a text on dimensional analysis for students of Aeronautics at this School. It develops the subject from a viewpoint which is inadequately treated in most standard texts hut which the author's experience has shown to be valuable to students and professionals alike. The analysis treats two types of consistent units, namely, fixed units and natural units. Fixed units include those encountered in the various familiar English and metric systems. Natural units are not fixed in magnitude once and for all but depend on certain physical reference parameters which change with the problem under consideration. Detailed rules are given for the orderly choice of such dimensional reference parameters and for their use in various applications. It is shown that when transformed into natural units, all physical quantities are reduced to dimensionless form. The dimension- less parameters of the well known Pi Theorem are shown to be in this category. An important corollary is proved, namely that any valid physical equation remains valid if all dimensional quantities in the equation be replaced by their dimensionless counterparts in any consistent system of natural units. -
Chapter 5 Dimensional Analysis and Similarity
Chapter 5 Dimensional Analysis and Similarity Motivation. In this chapter we discuss the planning, presentation, and interpretation of experimental data. We shall try to convince you that such data are best presented in dimensionless form. Experiments which might result in tables of output, or even mul- tiple volumes of tables, might be reduced to a single set of curves—or even a single curve—when suitably nondimensionalized. The technique for doing this is dimensional analysis. Chapter 3 presented gross control-volume balances of mass, momentum, and en- ergy which led to estimates of global parameters: mass flow, force, torque, total heat transfer. Chapter 4 presented infinitesimal balances which led to the basic partial dif- ferential equations of fluid flow and some particular solutions. These two chapters cov- ered analytical techniques, which are limited to fairly simple geometries and well- defined boundary conditions. Probably one-third of fluid-flow problems can be attacked in this analytical or theoretical manner. The other two-thirds of all fluid problems are too complex, both geometrically and physically, to be solved analytically. They must be tested by experiment. Their behav- ior is reported as experimental data. Such data are much more useful if they are ex- pressed in compact, economic form. Graphs are especially useful, since tabulated data cannot be absorbed, nor can the trends and rates of change be observed, by most en- gineering eyes. These are the motivations for dimensional analysis. The technique is traditional in fluid mechanics and is useful in all engineering and physical sciences, with notable uses also seen in the biological and social sciences. -
Lord Kelvin and the Age of the Earth.Pdf
ME201/MTH281/ME400/CHE400 Lord Kelvin and the Age of the Earth Lord Kelvin (1824 - 1907) 1. About Lord Kelvin Lord Kelvin was born William Thomson in Belfast Ireland in 1824. He attended Glasgow University from the age of 10, and later took his BA at Cambridge. He was appointed Professor of Natural Philosophy at Glasgow in 1846, a position he retained the rest of his life. He worked on a broad range of topics in physics, including thermody- namics, electricity and magnetism, hydrodynamics, atomic physics, and earth science. He also had a strong interest in practical problems, and in 1866 he was knighted for his work on the transtlantic cable. In 1892 he became Baron Kelvin, and this name survives as the name of the absolute temperature scale which he proposed in 1848. During his long career, Kelvin published more than 600 papers. He was elected to the Royal Society in 1851, and served as president of that organization from 1890 to 1895. The information in this section and the picture above were taken from a very useful web site called the MacTu- tor History of Mathematics Archive, sponsored by St. Andrews University. The web address is http://www-history.mcs.st-and.ac.uk/~history/ 2 kelvin.nb 2. The Age of the Earth The earth shows it age in many ways. Some techniques for estimating this age require us to observe the present state of a time-dependent process, and from that observation infer the time at which the process started. If we believe that the process started when the earth was formed, we get an estimate of the earth's age. -
Units and Magnitudes (Lecture Notes)
physics 8.701 topic 2 Frank Wilczek Units and Magnitudes (lecture notes) This lecture has two parts. The first part is mainly a practical guide to the measurement units that dominate the particle physics literature, and culture. The second part is a quasi-philosophical discussion of deep issues around unit systems, including a comparison of atomic, particle ("strong") and Planck units. For a more extended, profound treatment of the second part issues, see arxiv.org/pdf/0708.4361v1.pdf . Because special relativity and quantum mechanics permeate modern particle physics, it is useful to employ units so that c = ħ = 1. In other words, we report velocities as multiples the speed of light c, and actions (or equivalently angular momenta) as multiples of the rationalized Planck's constant ħ, which is the original Planck constant h divided by 2π. 27 August 2013 physics 8.701 topic 2 Frank Wilczek In classical physics one usually keeps separate units for mass, length and time. I invite you to think about why! (I'll give you my take on it later.) To bring out the "dimensional" features of particle physics units without excess baggage, it is helpful to keep track of powers of mass M, length L, and time T without regard to magnitudes, in the form When these are both set equal to 1, the M, L, T system collapses to just one independent dimension. So we can - and usually do - consider everything as having the units of some power of mass. Thus for energy we have while for momentum 27 August 2013 physics 8.701 topic 2 Frank Wilczek and for length so that energy and momentum have the units of mass, while length has the units of inverse mass. -
Electron-Positron Pairs in Physics and Astrophysics
Electron-positron pairs in physics and astrophysics: from heavy nuclei to black holes Remo Ruffini1,2,3, Gregory Vereshchagin1 and She-Sheng Xue1 1 ICRANet and ICRA, p.le della Repubblica 10, 65100 Pescara, Italy, 2 Dip. di Fisica, Universit`adi Roma “La Sapienza”, Piazzale Aldo Moro 5, I-00185 Roma, Italy, 3 ICRANet, Universit´ede Nice Sophia Antipolis, Grand Chˆateau, BP 2135, 28, avenue de Valrose, 06103 NICE CEDEX 2, France. Abstract Due to the interaction of physics and astrophysics we are witnessing in these years a splendid synthesis of theoretical, experimental and observational results originating from three fundamental physical processes. They were originally proposed by Dirac, by Breit and Wheeler and by Sauter, Heisenberg, Euler and Schwinger. For almost seventy years they have all three been followed by a continued effort of experimental verification on Earth-based experiments. The Dirac process, e+e 2γ, has been by − → far the most successful. It has obtained extremely accurate experimental verification and has led as well to an enormous number of new physics in possibly one of the most fruitful experimental avenues by introduction of storage rings in Frascati and followed by the largest accelerators worldwide: DESY, SLAC etc. The Breit–Wheeler process, 2γ e+e , although conceptually simple, being the inverse process of the Dirac one, → − has been by far one of the most difficult to be verified experimentally. Only recently, through the technology based on free electron X-ray laser and its numerous applications in Earth-based experiments, some first indications of its possible verification have been reached. The vacuum polarization process in strong electromagnetic field, pioneered by Sauter, Heisenberg, Euler and Schwinger, introduced the concept of critical electric 2 3 field Ec = mec /(e ). -
Three-Dimensional Analysis of the Hot-Spot Fuel Temperature in Pebble Bed and Prismatic Modular Reactors
Transactions of the Korean Nuclear Society Spring Meeting Chuncheon, Korea, May 25-26 2006 Three-Dimensional Analysis of the Hot-Spot Fuel Temperature in Pebble Bed and Prismatic Modular Reactors W. K. In,a S. W. Lee,a H. S. Lim,a W. J. Lee a a Korea Atomic Energy Research Institute, P. O. Box 105, Yuseong, Daejeon, Korea, 305-600, [email protected] 1. Introduction thousands of fuel particles. The pebble diameter is 60mm High temperature gas-cooled reactors(HTGR) have with a 5mm unfueled layer. Unstaggered and 2-D been reviewed as potential sources for future energy needs, staggered arrays of 3x3 pebbles as shown in Fig. 1 are particularly for a hydrogen production. Among the simulated to predict the temperature distribution in a hot- HTGRs, the pebble bed reactor(PBR) and a prismatic spot pebble core. Total number of nodes is 1,220,000 and modular reactor(PMR) are considered as the nuclear heat 1,060,000 for the unstaggered and staggered models, source in Korea’s nuclear hydrogen development and respectively. demonstration project. PBR uses coated fuel particles The GT-MHR(PMR) reactor core is loaded with an embedded in spherical graphite fuel pebbles. The fuel annular stack of hexahedral prismatic fuel assemblies, pebbles flow down through the core during an operation. which form 102 columns consisting of 10 fuel blocks PMR uses graphite fuel blocks which contain cylindrical stacked axially in each column. Each fuel block is a fuel compacts consisting of the fuel particles. The fuel triangular array of a fuel compact channel, a coolant blocks also contain coolant passages and locations for channel and a channel for a control rod. -
1.3.4 Atoms and Molecules Name Symbol Definition SI Unit
1.3.4 Atoms and molecules Name Symbol Definition SI unit Notes nucleon number, A 1 mass number proton number, Z 1 atomic number neutron number N N = A - Z 1 electron rest mass me kg (1) mass of atom, ma, m kg atomic mass 12 atomic mass constant mu mu = ma( C)/12 kg (1), (2) mass excess ∆ ∆ = ma - Amu kg elementary charge, e C proton charage Planck constant h J s Planck constant/2π h h = h/2π J s 2 2 Bohr radius a0 a0 = 4πε0 h /mee m -1 Rydberg constant R∞ R∞ = Eh/2hc m 2 fine structure constant α α = e /4πε0 h c 1 ionization energy Ei J electron affinity Eea J (1) Analogous symbols are used for other particles with subscripts: p for proton, n for neutron, a for atom, N for nucleus, etc. (2) mu is equal to the unified atomic mass unit, with symbol u, i.e. mu = 1 u. In biochemistry the name dalton, with symbol Da, is used for the unified atomic mass unit, although the name and symbols have not been accepted by CGPM. Chapter 1 - 1 Name Symbol Definition SI unit Notes electronegativity χ χ = ½(Ei +Eea) J (3) dissociation energy Ed, D J from the ground state D0 J (4) from the potential De J (4) minimum principal quantum n E = -hcR/n2 1 number (H atom) angular momentum see under Spectroscopy, section 3.5. quantum numbers -1 magnetic dipole m, µ Ep = -m⋅⋅⋅B J T (5) moment of a molecule magnetizability ξ m = ξB J T-2 of a molecule -1 Bohr magneton µB µB = eh/2me J T (3) The concept of electronegativity was intoduced by L. -
Arxiv:1706.03391V2 [Astro-Ph.CO] 12 Sep 2017
Insights into neutrino decoupling gleaned from considerations of the role of electron mass E. Grohs∗ Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA George M. Fuller Department of Physics, University of California, San Diego, La Jolla, California 92093, USA Abstract We present calculations showing how electron rest mass influences entropy flow, neutrino decoupling, and Big Bang Nucleosynthesis (BBN) in the early universe. To elucidate this physics and especially the sensitivity of BBN and related epochs to electron mass, we consider a parameter space of rest mass values larger and smaller than the accepted vacuum value. Electromagnetic equilibrium, coupled with the high entropy of the early universe, guarantees that significant numbers of electron-positron pairs are present, and dominate over the number of ionization electrons to temperatures much lower than the vacuum electron rest mass. Scattering between the electrons-positrons and the neutrinos largely controls the flow of entropy from the plasma into the neu- trino seas. Moreover, the number density of electron-positron-pair targets can be exponentially sensitive to the effective in-medium electron mass. This en- tropy flow influences the phasing of scale factor and temperature, the charged current weak-interaction-determined neutron-to-proton ratio, and the spectral distortions in the relic neutrino energy spectra. Our calculations show the sen- sitivity of the physics of this epoch to three separate effects: finite electron mass, finite-temperature quantum electrodynamic (QED) effects on the plasma equation of state, and Boltzmann neutrino energy transport. The ratio of neu- trino to plasma-component energy scales manifests in Cosmic Microwave Back- ground (CMB) observables, namely the baryon density and the radiation energy density, along with the primordial helium and deuterium abundances.