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Mechanics

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Fluids

Human powered vehicles operate in a fluid environment. The bicycle and rider interact with the air through which the system is moving and experience aerodynamic forces that increase quadratically with the air-speed.

A boat operates at the interface between two fluids, the water that provides the "lift" and some drag, and air. These fluids have different properties (density, viscosity, etc.,) and these must be understood in order to design an efficient boat. Options such as replacing the displacement hull with hydrofoils need tod be considered if high speed boats are to be designed.

Airplanes rely on the air to provide the lift required to keep them in flight. This fluid also contributes a drag force on the aircraft and as with the bicycle this increases as the square of the airspeed. The power required to maintain flight is close to the limit of human capability and the aircraft system requires a careful balance of lift and drag forces and perhaps flight close to the ground to take advantage of the "ground effect" if long distance flights are to be achieved.