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Friction, Drag and Air Resistance

When an object travels through a medium, it interacts with the particles in that medium. This can slow the object down or provide lift.

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  • Friction is the resistance to motion due to contact forces.
    • Usually, an object experiences friction due to collisions with particles in air or a rough surface of a solid.
  • Friction always opposes motion, meaning that it slows down moving objects.
  • Friction converts kinetic energy into other types of energy, mainly heat.
    • This is why brakes on a car can overheat if used too much.
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  • Drag is a frictional force.
  • Objects that travel through a liquid or gas experience drag.
  • Drag is due to collisions between the travelling object and the particles in the medium.
  • The faster an object moves through a medium, the larger the drag.
  • Drag is also affected by the shape of an object (how streamlined it is).
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Air resistance

  • Air resistance is a type of drag.
  • Air resistance is a frictional force which opposes the motion of an object travelling through air.

Lift on a Wing

A moving wing can experience lift. Lift is an upward force due to the collisions with air particles on the underside of the wing.

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Equal and opposite force

  • Lift is a result of Newton's Third Law of Motion:
    • Every action has an equal and opposite reaction.
  • The wing of a plane pushes air particles downward as it flies forward.
  • As a result of this downward force on the air particles, there is an equal and opposite upward force on the wing.
    • This force is called lift.
  • This is the basic principle of how aeroplanes fly.
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Shape of the wing

  • The wing is angled to maximise the amount of air it can push downwards, thereby generating the maximum force upwards.
  • The wing is also smooth and slightly curved to reduce drag forces and turbulence.

Jump to other topics

1Measurements & Errors

2Particles & Radiation


4Mechanics & Materials


6Further Mechanics & Thermal Physics (A2 only)

7Fields & Their Consequences (A2 only)

8Nuclear Physics (A2 only)

9Option: Astrophysics (A2 only)

10Option: Medical Physics (A2 only)

11Option: Engineering Physics (A2 only)

12Option: Turning Points in Physics (A2 only)

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