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Rolling resistance, sometimes called rolling friction or rolling drag, is the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface. It is mainly caused by non-elastic effects; that is, not all the energy needed for deformation (or movement) of the wheel, roadbed, etc., is recovered when the pressure is removed.
Hertz solved the contact problem in the absence of friction, for a simple geometry (curved surfaces with constant radii of curvature). Carter considered the rolling contact between a cylinder and a plane, as described above. A complete analytical solution is provided for the tangential traction.
Schematic of quantities for capstan equation An example of holding capstans and a powered capstan used to raise sails on a tall ship. The capstan equation [ 1 ] or belt friction equation , also known as Euler–Eytelwein formula [ 2 ] (after Leonhard Euler and Johann Albert Eytelwein ), [ 3 ] relates the hold-force to the load-force if a ...
rolling friction. In the case of bodies capable of rolling, there is a particular type of friction, in which the sliding phenomenon, typical of dynamic friction, does not occur, but there is also a force that opposes the motion, which also excludes the case of static friction. This type of friction is called rolling friction.
The friction coefficient is an empirical (experimentally measured) structural property that depends only on various aspects of the contacting materials, such as surface roughness. The coefficient of friction is not a function of mass or volume. For instance, a large aluminum block has the same coefficient of friction as a small aluminum block.
"Rolling friction/static friction is much greater than sliding friction. The coefficient of rolling/static friction is greater than that of sliding/kinetic friction. Static friction prevents motion. This is why car wheels roll to a stop instead of skidding in order to stop as soon as possible.
Braking distance refers to the distance a vehicle will travel from the point when its brakes are fully applied to when it comes to a complete stop. It is primarily affected by the original speed of the vehicle and the coefficient of friction between the tires and the road surface, [Note 1] and negligibly by the tires' rolling resistance and vehicle's air drag.
This may be the reason why the minimum in the coefficient of friction for a liquid-lubricated journal bearing was not discovered by him, but was demonstrated by the graphs of Martens and Stribeck. The graphs plotted by Martens show the coefficient of friction either as a function of pressure, speed or temperature (i.e. viscosity), but not of ...