Mass, conversion into energy

Barotropic a condition in a water mass whereby the surfaces of constant pressure are parallel to the surfaces of constant density in a state of barotropic stratification, no potential energy is available for conversion into kinetic energy. 

In order to determine the distributions of pressure, velocity, and temperature the principles of conservation of mass, conservation of momentum (Newton s Law) and conservation of energy (first law of Thermodynamics) are applied. These conservation principles represent empirical models of the behavior of the physical world. They do not, of course, always apply, e.g., there can be a conversion of mass into energy in some circumstances, but they are adequate for the analysis of the vast majority of engineering problems. These conservation principles lead to the so-called Continuity, Navier-Stokes and Energy equations respectively. These equations involve, beside the basic variables mentioned above, certain fluid properties, e.g., density, p viscosity, p conductivity, k and specific heat, cp. Therefore, to obtain the solution to the equations, the relations between these properties and the pressure and temperature have to be known. (Non-Newtonian fluids in which p depends on the velocity field are not considered here.) As discussed in the previous chapter, there are, however, many practical problems in which the variation of these properties across the flow field can be ignored, i.e., in which the fluid properties can be assumed to be constant in obtaining fire solution. Such solutions are termed constant... 

Positron decay occurs in proton-rich nuclei. In this case, the positron (or p+ particle) is originated by conversion of a proton into a neutron, along with the emission of a neutrino to conserve the energy. Positrons are the antiparticle of electrons. In a very fast process (10 12s), emitted positrons collide with an electron of a nearby atom and both particles disappear in a process called annihilation. The necessary conservation of mass and energy accounts for the transformation of the mass of both particles into energy, which is characteristically emitted in the form of two 511-keV photons almost in opposite directions. Consequently, positron emitters are used to label radiopharmaceuticals produced with diagnostic purposes by imaging. 

For macroscopic bodies such as a baseball, the increase in mass because of the added eneagy is so small that it is not measurable. It was not even discovered until the beginning of (he twentieth century. At atomic and subatomic levels, however, the conversion of a small quantity of matter into energy is very important It is the energy source of the Sun and the stars, (he atomic bomb, the hydrogen bomb, and nuclear power plants. 

In summary, if you can do all your work in SI, you need never be concerned about force-mass conversions (N = kg m/s ) or energy conversions (J = N-m=W s). If you are confronted with problems (or literature, or current U.S. legal definitions) involving the kgf, Ibf, cal, kcal, or Btu, you must follow the rules outlined above Always write down the dimensions, treat the dimensions as algebraic quantities, and multiply by 1 as often as needed to get the quantities into the desired set of units, using the appropriate values of the force-mass conversion factor and the thermal-mechanical energy conversion factor. Even in SI, if you stray from the basic units (m, kg, s, A, K, mol, and cd), you will need conversion factors such as... 

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