young's modulus

• stress $\sigma$


  a force per unit cross sectional area applied to a solid object

  • Nm^-2
  • same as pressure but pressure applies to liquids and gases
• strain $\epsilon$


  the extension per unit length of a solid object.

  unitless

  • often a % - 0.03 = 3%
  • extended 3% per metre of original length
• stress causes strain
• equation

  • y= $\frac{stress}{strain}$
  • stress = $\frac{force\ }{area\ }$
  • strain $\frac{extension}{length}$
  • y = $\frac{force\ \times length}{area\ \times extension}$