i. The modulus of elasticity is the slope of stress-strain diagram in the linearly elastic region
ii. Valid upto proportional limit only. Practically elastic and proportional limit are same.
1. Poisson’s Ratio,
i. The lateral strain
at any point in a bar is proportional to the axial strain 
at that same point if the material is linearly elastic.
ii. 
for all practical purpose 
