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Frictional contact mechanics emphasizes the effect of friction forces. Contact mechanics is part of mechanical engineering. The physical and mathematical formulation of the subject is built upon the mechanics of materials and continuum mechanics and focuses on computations involving elastic, viscoelastic, and plastic bodies in static or dynamic ...
For example, static friction can prevent an object from sliding down a sloped surface. The coefficient of static friction, typically denoted as μ s, is usually higher than the coefficient of kinetic friction. Static friction is considered to arise as the result of surface roughness features across multiple length scales at solid surfaces.
Stiction (a portmanteau of the words static and friction) [1] is the force that needs to be overcome to enable relative motion of stationary objects in contact. [2] Any solid objects pressing against each other (but not sliding) will require some threshold of force parallel to the surface of contact in order to overcome static adhesion. [3]
The static friction increases or decreases in response to the applied force up to an upper limit determined by the characteristics of the contact between the surface and the object. [ 3 ] A static equilibrium between two forces is the most usual way of measuring forces, using simple devices such as weighing scales and spring balances .
This theory is exact for the situation of an infinite friction coefficient in which case the slip area vanishes, and is approximative for non-vanishing creepages. It does assume Coulomb's friction law, which more or less requires (scrupulously) clean surfaces. This theory is for massive bodies such as the railway wheel-rail contact.
For example, a free body diagram of a block sitting upon an inclined plane can illustrate the combination of gravitational force, "normal" force, friction, and string tension. [ note 4 ] Newton's second law is sometimes presented as a definition of force, i.e., a force is that which exists when an inertial observer sees a body accelerating.
Air moving past an aircraft can lead to a buildup of charge called "precipitation static" or "P-static"; aircraft typically have one or more static wicks to remove it. [143] Checking the status of these is a standard task for pilots. [144] Similarly, helicopter blades move fast, and tribocharging can generate voltages up to 200 kV. [145]