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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.
Drag Forces. Drag forces are forces acting the opposite direction to an object moving through a fluid (either gas or liquid) Examples of drag forces are friction and air resistance. A key component of drag forces is it increases with the speed of the object. This is shown in the diagram below: Frictional forces on a car increase with its speed.
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.
15 Αυγ 2020 · Where $d$ = stopping distance, $v$ = velocity of object before encountering friction, $μ$ = the coefficient of friction and $g$ = acceleration due to gravity. In the case of vehicle braking distance, if the car is skidding you use the coefficient of kinetic friction between the tires and the road.
Athletes as well as car designers seek to reduce the drag force to lower their race times (Figure 6.29). Aerodynamic shaping of an automobile can reduce the drag force and thus increase a car’s gas mileage.
At highway speeds, over 50% of the power of a car is used to overcome air drag. The most fuel-efficient cruising speed is about 70–80 km/h (about 45–50 mi/h). For this reason, during the 1970s oil crisis in the United States, maximum speeds on highways were set at about 90 km/h (55 mi/h).
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.
