# Physics on the go Materials Section 1

Section 1 of Materials focuisng on the Young Modulus, Stress and Strain and Hooke's Law

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- Created by: Edward
- Created on: 27-12-12 14:07

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- Materials Section 1
- Hooke's Law
- Extension is proportional to force
- F=ke
- Extension is proportional to force
- F=force (N)
- k=stiffness/spring constant
- e=extension (m)

- Elastic deformation
- Material returns to its original shape after being stretched
- Atoms return to their equilibrium distance apart

- Material returns to its original shape after being stretched
- Plastic deformation
- Material does not return to its original shape, permanently stretched
- Atoms don't return to their original positions

- Material does not return to its original shape, permanently stretched
- Tensile force +
- Stretch the spring

- Compressive forces -
- Squash the spring

- Stress (Pa)
- f/a
- f=force applied (N)
- a=cross sectional area (m^2)

- The force per unit area of a material
- Breaking stress
- When the atoms in the material separate completely, breaking the material

- Ultimate Tensile Stress (UTS)
- The maximum stress the material can withstand

- f/a
- Strain
- e/l
- e=extension (m)
- l=original length of material (m)

- The extension per unit length
- Elastic Strain Energy
- Energy stored in a stretched material
- Before the elastic limit, all the work done in stretching is stored as potential energy
- This is called elastic strain energy
- Is the area under the graph of a force extension graph
- E =0.5(ke^2)
- k=stiffness/spring constant
- e=extension (m)

- This is called elastic strain energy

- e/l
- The Young Modulus (Pa)
- Tensile stress /Tensile Strain
- Stress/strain graph
- The Young Modulus is the gradient of a stress/strain graph
- Area under the graph gives the strain energy
- energy=0.5x stress x strain

- Hooke's Law

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