... investigation. 1.2 Background and Theory Relative motion between a body and a fluid (when a body moves through a fluid at rest or when a fluid flows over a body) causes a force on the body. The horizontal component of this force is the drag and the vertical component is the lift. The magnitude of these forces depends on numerous factors. Those to do with the body; the shape, attitude, size and in some cases the surface roughness. Those concerning the fluid; density, viscosity, unsteadiness and turbulence in the fluid stream. The velocity of the relative motion is also important (if high enough to approach the speed of sound in the fluid). However, during this experiment surface roughness, unsteady and turbulent flow cannot be investigated and the velocities are low compared to the speed of sound in the fluid. Under these conditions the force felt at a particular attitude can be written as ...

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