Materials

• Density of a material


  Mass per unit volume
• Density equation


  Mass / Volume
• Units of density


  Kgm^-3
• When an object is submerged what is the upthrust


  The upthrust is equal to the weight of the fluid that it displaces
• What determines whether an object sinks or floats

  The balance between the weight and upthrust of the object as if the weight exceeds upthrust the object will sink
• Why would a uniform object with a density greater than the liquid its in will sink?


  • Upthrust will be equal to the weight of the liquid displaced
  • Maximum upthrust will equal the density of fluid x volume of object x gravitational field strength
  • Weight of the object is equal to the density of the object x volume of the object x gravitational field strength
  • If an objects density is greater the weight will always be greater than the upthrust and the object will sink
• What objects does stokes law apply to


  Small spherical objects
• What flow is needed for stokes law


  Laminar flow
• What can you calculate from stokes law


  The viscous drag force that a small spherical object experiences when falling at low speeds through a viscous fluid with laminar flow
• Stokes law equation


  F = 6(pi)nrv
• What is elastic deformation


  An object that returns to its orginial shape after the deforming forces are removed
• What is plastic deformation


  When an object no longer returns to its original shape after deforming forces are removed
• Hookes law


  The extension of an elastic object that is directly proportional to the force thats applied to it up until its limit of proportionality
• What is the limit of proportionality


  The point beyond which the force and extension will no longer be directly proportional - hookes law is no longer obeyed
• Whats the elastic limit


  The point beyond which the object will no longer elastically deform and will deform plastically instead
• Hookes law equation 


  F = kx
• Whats mechanical stress


  The force experienced by an object per unit area
• Stress equation


  Stress = F / A
• Strain equation


  Strain = Change in length / length
• Whats the young modulus tell you 


  A materials young modulus is a measure of how much force is required for a given extension regardless of the objects dimension
• Young modulus equation


  Young modulus = Stress / Strain
• Whats breaking stress


  Breaking stress is the maximum stress that an object can withstand before fracturing
• Whats the yield point


  The point beyond which the object will experience a large extension without a substantial increase in the force applied
• What type of energy is stored in an object that has been stretched

  Elastic potential energy
• What does the gradient and area represent on a force - extension graphs


  • Gradient represents the elastic constant
  • Area is equal to elastic potential energy stored in the spring
• Whats the gradient represent on a stress-strain graph


  • gradient represents of the young modulus of the material
• What is tensile strain


  An increase in length compared to original length
• What is compressive strain


  A decrease in length compared to the original length
• What is laminar flow


  Different layers of a fluid flow at different speeds but thr layers dont cross or mix
• Conditions for laminar flow


  • Layers dont cross or mix
  • Layers are always parallel
  • Often occurs with slower flow speeds
• What is turbulent flow


  Different layers of a fluid flowing at different speeds and crossing paths, mixing and forming vertices
• Conditions for turbulent flow


  • Layers will always mix and cross over
  • Vertices will often be present
  • Often occur at higher speeds
  • Often occur in more viscous fluids
• What is viscosity


  Viscosity is a measure of hw slowly a material flows
• What happens to viscosity as temperature of a fluid increases


  The viscosity of the fluid will decrease so the fluid will flow faster