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The friction drag force, which is a tangential force on the aircraft surface, depends substantially on boundary layer configuration and viscosity. The net friction drag, , is calculated as the downstream projection of the viscous forces evaluated over the body's surface.
The force on an object that resists its motion through a fluid is called drag. When the fluid is a gas like air, it is called aerodynamic drag or air resistance. When the fluid is a liquid like water it is called hydrodynamic drag, but never "water resistance". Fluids are characterized by their ability to flow.
For most large objects such as bicyclists, cars, and baseballs not moving too slowly, the magnitude of the drag force \(F_D\) is found to be proportional to the square of the speed of the object. We can write this relationship mathematically as \(F_D\propto v^2 \).
As the vehicle moves forwards through the air the air rushes past the vehicle. This causes friction, which we call drag, and this slows the vehicle down. Large amounts of money are spent by the designers of cars to try and make a car which has a little drag as possible.
Air friction, or air drag, is an example of fluid friction. Unlike the standard model of surface friction, such friction forces are velocity dependent. The velocity dependence may be very complicated, and only special cases can be treated analytically.
4 Μαρ 2017 · The forces that a moving vehicle must overcome are the tire rolling resistance, the driveline friction, elevation, vehicle acceleration changes, and also aerodynamics. Let us assume that the vehicle moves along a flat surface at a constant speed and the external forces are limited to the tire friction and to the aerodynamic drag.
2 Μαΐ 2017 · Friction tries to reduce (kinetic friction) or prevent (static friction) relative motion between two bodies. Think about a car starting from rest on the flat. To do that the frictional force on the tyre due to the ground must be in the forward direction.
