Young's modulus

Intermediate

Stiffness for tension or compression.

Key relationY = σ/ε

Y = stress/strain for tension or compression. Steel 200 GPa, aluminium 70 GPa, rubber ~0.01 GPa. A stiff material has high Y.

Worked example

1 mm² steel wire (L = 2 m) under 100 N stretches 1 mm.

Common mistake

ΔL = FL/AY.

In more detail

Young's modulus E = stress/strain describes how stiff a material is in tension or compression. Steel has a Young's modulus of about 200 GPa, and rubber is much lower.

Real-world uses

Engineers select materials with high Young's modulus for stiff structures.
Rubber's low modulus makes it suitable for seals and tyres.
Engineers choose materials for bridges and skyscrapers by comparing their Young's modulus values.

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Frequently asked questions

What is the unit?

The pascal, usually quoted in gigapascals for solids.

Is a high modulus always good?

For stiffness, yes, but materials must also resist fracture and fatigue.

Is a higher Young's modulus always better?

For stiff structures, yes. But many designs also need toughness and resistance to fracture, which Young's modulus does not measure.

Young's modulus

In more detail

Real-world uses

Frequently asked questions

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