What is an atomic nucleus? the outer part of an atom in which electrons move
the outer part of an atom in which neutrons move
the central part of an atom, composed of protons and neutrons
the central part of an atom, composed of protons and electrons

gravity causes stares to cluster i think so

the answer would be b i believe

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.