Professor Saltzman introduces the material properties of elasticity and viscosity. He describes two separate experimental setups to measure the elasticity and the viscosity of a material. Material elasticity can be defined in terms of stress-strain property, and defines the Young's modulus (E), which is the slope of the stress-strain curve. Fluid viscosity, on the other hand, is described by shear stress. When modeling any material, the spring can be used to represent an ideal elastic material and the dashpot an ideal viscoelastic material. All biomaterials contain some combination of these properties and can be described by physical models that consist of both spring and dashpot.