Drag
• This is force causing resistance in water or in the air.
• Drag acts in the opposite direction to the movement of the object.
Surface Drag:
• This type of drag depends mainly on the surface moving through the fluid.
E.g) rough surfaces (scratched cricket ball) or smooth surfaces (shaving the body in
swimming).
Form Drag:
• This type of drag depends on the cross-sectional area of the body exposed to the
fluid (cyclist crouched down low) - creates less drag.
• In water, drag will depend on how the swimmer “lies” in the water - if their hips
sink too low the drag increases.
• Planning refers to skimming or gliding over the water surface as opposed to plowing
through the water like a boat would.
• This is found in sports like wind surfing.
• A swimmer wants to maximise propulsion while minimising drag so that the body can
move through the water as efficiently as possible.
• There are 4 primary forces that act on swimmers:
1. Thrust
2. Drag -> pressure drag & skin friction drag
3. Weight
4. Buoyancy
• The weight of the swimmer is offset by buoyancy and through the arm strokes and
kick.
• By pressing down on the water, an equal and opposite reaction occurs which lifts
the swimmer higher in the water.
• Pressure drag: results from water resistance over the swimmers frontal are and the
flow separation which occurs behind the swimmer.
• Therefore, a swimmer must streamline their body to reduce the amount of
separation.
• This is force causing resistance in water or in the air.
• Drag acts in the opposite direction to the movement of the object.
Surface Drag:
• This type of drag depends mainly on the surface moving through the fluid.
E.g) rough surfaces (scratched cricket ball) or smooth surfaces (shaving the body in
swimming).
Form Drag:
• This type of drag depends on the cross-sectional area of the body exposed to the
fluid (cyclist crouched down low) - creates less drag.
• In water, drag will depend on how the swimmer “lies” in the water - if their hips
sink too low the drag increases.
• Planning refers to skimming or gliding over the water surface as opposed to plowing
through the water like a boat would.
• This is found in sports like wind surfing.
• A swimmer wants to maximise propulsion while minimising drag so that the body can
move through the water as efficiently as possible.
• There are 4 primary forces that act on swimmers:
1. Thrust
2. Drag -> pressure drag & skin friction drag
3. Weight
4. Buoyancy
• The weight of the swimmer is offset by buoyancy and through the arm strokes and
kick.
• By pressing down on the water, an equal and opposite reaction occurs which lifts
the swimmer higher in the water.
• Pressure drag: results from water resistance over the swimmers frontal are and the
flow separation which occurs behind the swimmer.
• Therefore, a swimmer must streamline their body to reduce the amount of
separation.
