Young's modulus
A measure of the stiffness of a material, defined as E = stress / strain = (F/A) / (Δx/x), where F is force, A is cross-sectional area, Δx is extension, and x is original length. Measured in pascals (Pa). Materials with high Young's modulus are stiffer (resist deformation); those with low Young's modulus are more easily deformed.
Formula
E = σ/ε = (F/A)/(Δx/x)
Real World
Engineers designing the Shard in London used steel with a Young's modulus of ~200 GPa, ensuring the structure flexes only microscopically under wind loads rather than swaying dangerously.
Exam Focus
Always state units (Pa or GPa) and show stress divided by strain — not force divided by extension — for full marks.
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