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Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other. [7] [8] Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces. [9] [10] [11] Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body.
Without friction to dissipate a body's energy into heat, the body's energy will trade between potential and (non-thermal) kinetic forms while the total amount remains constant. Any gain of kinetic energy, which occurs when the net force on the body accelerates it to a higher speed, must be accompanied by a loss of potential energy.
Stokes' law is the basis of the falling-sphere viscometer, in which the fluid is stationary in a vertical glass tube.A sphere of known size and density is allowed to descend through the liquid.
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 .
coefficient of friction: unitless (dynamic) viscosity (also ) pascal second (Pa⋅s) permeability (electromagnetism) henry per meter (H/m) reduced mass: kilogram (kg) Standard gravitational parameter: cubic meter per second squared mu nought Vacuum permeability or the magnetic constant
In physics, Hooke's law is an empirical law which states that the force (F) needed to extend or compress a spring by some distance (x) scales linearly with respect to that distance—that is, F s = kx, where k is a constant factor characteristic of the spring (i.e., its stiffness), and x is small compared to the total possible deformation of the spring.
The friction drag force, which is a tangential force on the aircraft surface, depends substantially on boundary layer configuration and viscosity. The net friction drag, , is calculated as the downstream projection of the viscous forces evaluated over the body's surface. The sum of friction drag and pressure (form) drag is called viscous drag.
There are two main descriptions of motion: dynamics and kinematics.Dynamics is general, since the momenta, forces and energy of the particles are taken into account. In this instance, sometimes the term dynamics refers to the differential equations that the system satisfies (e.g., Newton's second law or Euler–Lagrange equations), and sometimes to the solutions to those equations.