(a) for the solidification of iron, calculate the critical radius r* and the activation free energy δg* if nucleation is homogeneous. values for the latent heat of fusion and surface free energy are –1.85 × 109 j/m3 and 0.204 j/m2, respectively. use the supercooling value δt = 273 k, and the melting point of iron is 1538°c.

Plot schematically the tensile stress versus strain curves for a typical thermoplastic material at a temperature below its glass transition temperature (tg and at a temperature above its tg, respectively. do the same for a typical thermosetting material. list in a table any differences or similarities between the two materials at t> tg and t < tg, respectively, and relate them to the structures of the two types of polymers