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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.
13 Οκτ 2018 · With gravity being lower, the force of friction at the contact point is reduced, while the force forward is still the same. This means that the wheel does not "feel" enough friction at its contact point to gain the necessary torque (it doesn't turn fast enough), and hence slips.
For instance, consider a skydiver falling through air under the influence of gravity. The two forces acting on him are the force of gravity and the drag force (ignoring the buoyant force). The downward force of gravity remains constant regardless of the velocity at which the person is moving.
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.
For instance, consider a skydiver falling through air under the influence of gravity. The two forces acting on him are the force of gravity and the drag force (ignoring the small buoyant force). The downward force of gravity remains constant regardless of the velocity at which the person is moving.
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.