friction

• friction

  a force that opposes motion
• 2 main types of friction

  • contact friction (between 2 or more solid surfaces)
  • fluid friction - through either liquid or gas (drag/fluid resistance/air resistance)
• 3 things affecting fluid friction 


  • the force depends on viscosity (thickness) of fluid
  • force increases as speed increases
  • the force depends on size and shape of the object - larger the object the more resistance it will meet
• 3 things about frictional forces

  • always act in opposite direction to motion
  • can never speed things up or start moving
  • they convert kinetic energy into heat