We done an experiment of tensile test where we used the testometric machine that pulls different kind of material (aluminium, PVC, steel, brass) and generated graph stress/strain and etc, now we come to these questions: 1. Explain why the plastics/ polymer has a lower modulus and strength than the metal. 2. Explain what is happening at the atomic (or molecular) level in the elastic region and the plastic region of each material. Can anyone provides complete answers? Thanks!