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31 Μαΐ 2014 · (Air) friction on a pendulum definitely changes with time - because even in a simple model, it is a function of velocity. A simple expression for the friction would have the force proportional to $$F = av + bv^2 $$
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.
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.
2 Μαΐ 2017 · For a car travelling down a hill with constant velocity, the component of the gravitational force which is parallel to the cars velocity must be equal and opposite to the frictional force, whereby the frictional force opposes the motion of the car.
Friction arises in part because of the roughness of the surfaces in contact, as seen in the expanded view. For the object to move, it must rise to where the peaks of the top surface can skip along the bottom surface. Thus, a force is required just to set the object in motion.
2 Ιαν 2018 · These frictional forces tend to be higher at higher speeds, (such as air resistance, which equals $kv^2$) which will indeed mean that the driving force has to be slightly higher. But either way, if the car is traveling at a constant speed, these forces will cancel and the "oomph" should be the same.
21 Οκτ 2024 · 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.
