# 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
• 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
• Plastic deformation
• 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
• 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)
• 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