Drag Forces (Oxford AQA IGCSE Physics)

Drag Forces

• Fluids are a category of substance which includes gases and liquids

• The particles in a fluid are free to move around

• When an object moves through a fluid, the object experiences friction as it collides with the particles in the gas or the liquid

• This type of friction is called drag

• Friction opposes the motion of the object, causing

  • Deceleration

  • Heating

• The denser the fluid the greater the drag force

  • For example, walking through air is easier than walking through water

Moving through fluids of different densities

• Air resistance is a specific type of drag

  • When objects move through air, they collide with the air particles and experience friction

• If the object's speed through the fluid increases, the frictional (drag) force also increases

  • Colloquially, when running one experiences a greater air resistance than when walking

  • This is caused by a greater speed through the fluid

  • More fluid particles collide with a faster object every second, so the force is greater