Work Done & Friction (AQA GCSE Physics)

• Friction is a force that works in opposition to the motion of an object
  • This slows down the motion of the object

• When friction is present, energy is transferred by heating
  • This raises the temperature (energy is transferred to the thermal store) of the object and its surroundings
  • The work done against the frictional forces causes this rise in the temperature

• Imperfections at the interface between the object and the surface bump into and rub up against each other
  • Not only does this slow the object down but also causes a transfer of energy to the thermal store of the object and the surroundings

The interface between the ground and the sledge is bumpy which is the source of the frictional force

Air Resistance

• Air resistance is a type of friction that slows the motion of an object
• Particles bump into the object as it moves through the air
  • As a result, energy is transferred by heating due to the work done against the frictional forces

The return module of a rocket heats up due to the work done by air resistance as it travels a distance through the atmosphere