Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: spook1456 on 16/04/2011 15:57:38
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the correct answer is .....will be revealed when poll ends
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Is it cheating if you looked it up on the internet before answering? [::)]
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That depends upon what you are trying to establish by the test, if you want to establish what proportion of people already know the correct answer it is better if they are required to do no research but if you want to test what proportion have an interest in the matter research should be encouraged.
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And atomic mass (symbol: u) is used in chemistry for defining the Atoms with the same number of protons, but differing numbers of neutrons. Also called isotopes they are different forms of a single element.
" It is defined as one twelfth of the rest mass of an unbound atom of carbon-12 in its nuclear and electronic ground state, and has a value of 1.660538782(83)×10−27 kg.
One Da (dalton) is approximately equal to the mass of one proton or one neutron. The CIPM have categorised it as a "non-SI unit whose values in SI units must be obtained experimentally"."
And "For things made up of many parts, like an atomic nucleus, planet, or star, the relativistic mass is the sum of the relativistic masses (or energies) of the parts, because energies are additive in closed systems. This is not true in systems which are open, however, if energy is subtracted. For example, if a system is bound by attractive forces and the work they do in attraction is removed from the system, mass will be lost. Such work is a form of energy which itself has mass, and thus mass is removed from the system, as it is bound. For example, the mass of an atomic nucleus is less than the total mass of the protons and neutrons that make it up, but this is only true after the energy (work) of binding has been removed in the form of a gamma ray (which in this system, carries away the mass of binding). This mass decrease is also equivalent to the energy required to break up the nucleus into individual protons and neutrons (in this case, work and mass would need to be supplied). Similarly, the mass of the solar system is slightly less than the masses of sun and planets individually." "Notice that the mass of the carbon atom is LESS than the mass of the sum of its parts! When a single carbon atom is formed from its separate parts, the mass of the total is LESS than those parts separately. This means that when an atom is formed from its parts SOME of the initial mass is LOST. This missing mass is called the "nuclear mass defect.""
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Yoron, please remember to include references to any quotations you include in your replies.