Two small aluminum spheres, each of mass 0.0250 kilograms, areseparated by 80.0 centimeters.
how many electrons does each sphere contain? (the atomic mass ofaluminum is 26.982 grams per mole, and its atomic number is13.)
how many electrons would have to be removed from one sphere andadded to the other to cause an attractive force between the spheresof magnitude 1.00*10^{4}n}(roughly one ton)? assume that the spheres may be treated as pointcharges.
what fraction of all the electrons in one of the spheres does thisrepresent?

Asteel tube (k=50 w/mk) of inner and outer diameter di = 20mm and do=26mm, respectively, is used to transfer heat from hot gases flowing over the tube (h-hot = 200w/m2k) to cold water flowing through the tube (h-cold = 8000 w/m2k). what is the cold-side overall heat transfer coefficient uc? to enhance heat transfer 16 straight fins of rectangular profile are installed longitudinally along the outer surface of the tube. the fins are equally spaced around the circumference of the tube, each having a thickness of 2mm and a length of 15mm. what is the corresponding overall heat transfer coefficient uc? *solve for uc in both cases*