write about the Friction in Solids:
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Whenever the surface of one body slides ver another, each body exerts a certain amount of force on other body. These forces are tangential to the surfaces. The force on each body is opposite to the direction of motion between two bodies. It prevents or opposes the relative motion between two bodies. It is common experience that an object placed on any surface does not move easily when a small force is applied to it. This is because of certain force of opposition acting between the surface of the object and the surface on which it is placed. Even a rolling ball comes to rest after covering a finite distance on playground because of such opposing force. Our foot ware is provided with designs at the bottom of its sole so as to produce force of opposition to avoid slipping. It is difficult to walk without such opposing force. You know what happens when you try to walk fast on polished flooring at home with soap water spread on it. There is a possibility of slipping due to lack of force of opposition. To initiate any motion between pair of surfaces, We need a certain minimum force. Also after the motion begins, it is constantly opposed by some natural force. This mechanical force between two solid surfaces in contact with each her is called as frictional force. The property which resists the relative motion between two surfaces in contact is called friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. ... Dry friction is subdivided into static friction ("stiction") between non-moving surfaces, and kinetic friction between moving surfaces.