Q2a. Write briefly on the following: I. Proof Resilience II. Strain Energy III. Impact Loading IV. Modulus of Resilience V. Obliquity and how it is determined VI. Principal plane VII. Mohr's Circle

Here's a brief explanation for Q2a.II:

II. Strain Energy
Strain energy is the energy stored within a material due to deformation caused by applied external forces. This energy is recoverable if the material remains within its elastic limit, meaning it will return to its original shape once the load is removed. It is typically expressed as the area under the stress-strain curve up to the point of deformation.