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Slip is defined such that a 2% slip means that the circumferential speed of the driving wheel exceeds the speed of the vehicle by 2%. A small percentage slip can result in a slip resistance which is much larger than the basic rolling resistance.
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.
The more regular the lattice is, the less disturbance happens and thus the less resistance. The amount of resistance is thus mainly caused by two factors. First, it is caused by the temperature and thus amount of vibration of the crystal lattice. Higher temperatures cause bigger vibrations, which act as irregularities in the lattice.
If the resistance is not constant, the previous equation cannot be called Ohm's law, but it can still be used as a definition of static/DC resistance. [4] Ohm's law is an empirical relation which accurately describes the conductivity of the vast majority of electrically conductive materials over many orders of magnitude of current.
Generally the force of rolling resistance is less than that associated with kinetic friction. [74] Typical values for the coefficient of rolling resistance are 0.001. [75] One of the most common examples of rolling resistance is the movement of motor vehicle tires on a road, a process which generates heat and sound as by-products. [76]
Unlike other resistive forces, drag force depends on velocity. [2] [3] This is because drag force is proportional to the velocity for low-speed flow and the velocity squared for high-speed flow. This distinction between low and high-speed flow is measured by the Reynolds number.
The electron mobility is defined by the equation: =. where: E is the magnitude of the electric field applied to a material, v d is the magnitude of the electron drift velocity (in other words, the electron drift speed) caused by the electric field, and; μ e is the electron mobility.
Curve resistance depends on various factors, the most important being the radius and the superelevation of a curve. Since curves are usually banked by superelevation, there will exist some speed at which there will be no sideways force on the train and where therefore curve resistance is minimum. At higher or lower speeds, curve resistance may ...