I/GCSE Physics: Stress, strain and the Young modulus

In I/GCSE Physics, do you guys still remember what stress, strain and the Young modulus is?

TENSILE FORCE – puts something in tension, i.e. tends to pull it apart

• If we consider tensile force per unit area, this takes into account the samples area of cross-section
• If we consider extension per unit length, this takes into account the length of the sample
• Tensile force per unit area = tensile stress (Nmor Pa) = tensile force / area of cross- section
• Tensile strength = the tensile stress at which the material breaks
• When it comes to I/GCSE Physics, Extension per unit length = tensile strain = Extension / original length
• Many materials, mainly metals, are found to obey Hooke’s law for small tensile strains. Under these circumstances,

the quantity: tensile stress / tensile strain
This quantity is the YOUNG MODULUS (Nm-2 or Pa)

• The STIFFER a material, the GREATER its Young modulus

• In I/GCSE Physics, as the stress increases, the sample begins NECKING – narrowing at one point
• Elastic limit – at this point the material stops behaving elastically and begins to behave plastically. When the stress is removed, the material does not return to its original length
• Yield point – the material shows a large increase in strain for a small increase in stress
• Plastic zone – the extension increases rapidly for small increase in force in this region. Solids which behave in this way are DUCTILE

That's all~ Thanks for watching.

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