forces and matter

• stretching, bending and compressing

  • must have more then one force or the object will go in the force's direction
• compress

  • forces inwards from opposite sides of the object
• stretching

  • one end of the spring is fixed at a point while it is pulled at the other end
• elastic deformation

  • the object returns to its original shape when load has been removed
• plastic deformation - distortions

  • object does not return to original shape when load is removed
• Hooke's law

  • spring constant k = force required to extend a spring per meter
  • F = KX
  • force = spring constant x extension
• Hooke's law

  • extension of a spring is directly proportional to force applied
• extension graph

  • elastic limit is the end of Hooke's law
  • rest is plastic deformation
  • if small slope - it is easy to stretch
  • if it is only linear it is brittle and snaps instead of stretching

  
• work done on graph

  • area under the graph
  • 0.5kx$^2$
• atmospheric pressure

  • total weight of the air above a unit area at a certain altitude
  • decreases the higher you get
  • as there are fewer air molecules then below
• pressure in a fluid

  • gas or liquid
  • pressure of gas depends on atmospheric pressure
  • air exerts an inward force on the outer surface of the object
  • if this is greater then the outward force of the particles inside then it will collapse
  • if outward force is greater it will expand
  • increasing the pressure inside the object increases collisions on the surface increasing pressure and force inside expanding the object
• pressure in a fluid example

  • increasing the particles inside a balloon by blowing into it
  • causes it to expand as there is higher pressure
  • this means there is higher force
• pressure in liquids

  • deeper in a fluid the higher pressure
  • as there is a greater amount of fluid above the object
  • leading to greater weight
  • therefor, also greater force felt
  • leading to greater pressure
• pressure in a liquid

  • denser the fluid the more pressure
  • mass = density x volume
  • means that weight is greater with density
  • leading to more force
  • leading to more pressure
• floating

  • floats if its weight is less then the weight of water it has displaced
• buoyancy force - upthrust

  • upwards force that counteracts weight of floating object
  • equal to weight of fluid displaced by the object
• buoyancy example

  • ball floats on water as its density is less than water
  • weight of the ball is less then the amount of water displaced
• pressure due to a column of liquid =

  height of column x density of liquid x g