Along cylindrical wood log (k = 0.17 w/m∙k and α = 1.28 × 10−7 m2/s) is 10 cm in diameter and is initially at a uniform temperature of 15°c. it is exposed to hot gases at 550°c in a fireplace with a heat transfer coefficient of 13.6 w/m^2∙k on the surface. if the ignition temperature of the wood is 420°c, determine how long it will be before the log ignites.

An  atom  (ours, not carroll's) consists of a positively charged  nucleus, surrounded by one or more negatively charged particles called  electrons. the positive charges equal the negative charges, so the atom has no overall charge; it is electrically neutral. most of an atom's mass is in its nucleus; the mass of an electron is only 1/1836 the mass of the lightest nucleus, that of hydrogen. although the nucleus is heavy, it is quite small compared with the overall size of an atom. the radius of a typical atom is around 0.1 to 0.25 nanometres (nm), whereas the radius of a nucleus is about 10-6  nm.  *  if an atom were enlarged to the size of the earth, its nucleus would be only 200 feet in diameter and could easily rest inside a small football stadium.read more on -

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