Poisson S Ratio — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Poisson's Ratio Valid for linear elastic, isotropic materials within the elastic limit. Define Longitudinal Strain l = L / L Define Transverse Strain t = d / d Observe experimentally that elongation in one direction causes contraction in perpendicular directions. Define Poisson's Ratio as the negative ratio to ensure a positive material constant for normal materials: = -( t / l) Material must be within its proportional limit (Hooke's Law region). Material is assumed to be isotropic. Theoretical range is -1 < 0.5 Practical range for most solids is 0 0.5 Believing Poisson's ratio must be 0.5 (this is only true for perfectly incompressible materials like ideal rubber). Forgetting the negative sign in the formula (since transverse strain is negative during tension, the negative sign makes the ratio positive). Confusing stress with strain in the ratio.