1. The radius of Fe atom is 0.1241 nm. Find (111) planar density of -Fe.

2. During tensile tests, strain hardening was observed for a metal alloy with a tensile strength of 18,000 psi under regular yielding condition. However, when it was pre-stretched to a 0.5% extension (based on the initial length of the specimen), its strength increased to 20,000 psi. If the pre-extension is increased to 5%, what could be the strength of the material?

3. A single cubic crystal is subjected to the plane stresses: x=80 MPa, xy=50 MPa, y=0 MPa. Find the resolved shear stress on (111) plane along the [101] direction. (first 1 in [101] has a bar over it)