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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.
The magnitude of the frictional force has two forms: one for static situations (static friction), the other for situations involving motion (kinetic friction). What follows is an approximate empirical (experimentally determined) model only.
For a body rolling uniformly, friction is zero in the absence of other forces. When a car accelerates, the friction force is forwards. For a body to accelerate, there must be an external force. There are two external forces here, gravity (useless for forward acceleration), and friction.
Friction is a force that opposes relative motion between systems in contact. One of the simpler characteristics of friction is that it is parallel to the contact surface between systems and always in a direction that opposes motion or attempted motion of the systems relative to each other.
17 Φεβ 2023 · Friction or frictional force is defined as the force that resists an object’s motion on a surface. The object can either be stationary or in motion relative to the surface. Friction occurs where the object is in contact with the surface.
21 Οκτ 2024 · When an object is dropped, it accelerates toward the center of Earth. Newton’s second law states that a net force on an object is responsible for its acceleration. If air resistance is negligible, the net force on a falling object is the gravitational force, commonly called its weight, \(w\).
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.
