Αποτελέσματα Αναζήτησης
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 is the friction from fluids like air and water. A runner feels the force of aerodynamic drag. A swimmer feels the force of hydrodynamic drag.
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.
In a car, the treads do not move with respect to the ground for the duration of their contact, so there is no relative motion to oppose. The friction is free to choose its direction based on the other forces. So, in each of your cases, the frictional force will be (mass of car)x(acceleration) forwards.
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 \(F_D\propto v^2 \).
The optimal aerodynamic shape, which has the lower drag coefficient is the shape of a water drop (Cd = 0.04). Due to the air friction, the water drop is forced to take the shape which has lowest resistance in contact with the air, hence it has the lowest drag coefficient.
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.
