Introduction, Types And Friction Of Horizontal Surface
FRICTION
Introduction:
The classic rules of sliding friction were discovered by Leonardo da Vinci (1452–1519) but remained unpublished in his notebooks. They were rediscovered by Guillaume Amontons (1699). Amontons presented the nature of friction in terms of surface irregularities and the force required to raise the weight pressing the surfaces together. This view was further elaborated by Belidor (representation of rough surfaces with spherical asperities, 1737) and Leonhard Euler (1750) who derived the angle of repose of a weight on an inclined plane and first distinguished between static and kinetic friction.
A different explanation was provided by Desaguliers (1725), who demonstrated the strong cohesion forces between lead spheres of which a small cap is cut off and which were then brought into contact with each other.
FRICTION
It is a well known phenomenon in the universe that anybody which is in a state of motion on any plane, left to itself, automatically comes to rest after travelling through some distance. This is due to the fact that some opposing force comes into play between the two surfaces which are in contact. This opposing force is called frictional force. This frictional force is always tangential to the surfaces in contact, and acts in a direction opposite to the relative motion of the body. Friction also exists even when the bodies do not move over each other
The force which comes to act along the direction tangential to the surfaces in contact and opposes the relative motion is called frictional force or simply friction.
CAUSES OF FRICTION:
When seen under a powerful microscope, every surface appears uneven with a number of depressions and elevations. When a body is placed on the surface of the another body, the elevations of the first body set into the depressions of the another body. It means that there is an interlocking of the surfaces of the two bodies. Automatically this causes an opposite force which resists the motion of one body over the other body. When an external force is applied, these depressions and elevations are sheared off and the body slides over the surface. Hence the pulling or sliding force encounters an opposition force. This opposition to slide the body on any surface is mentioned as sliding friction.
Figure shows how the interlocking of elevations and depressions occur between the surfaces of contact, when a body rests on a surface. When the body is set to move over a surface it encounteres continuously the frictional force.
The force which opposes the sliding or relative motion of two bodies in contact with each other, is called frictional force.
Frictional force some times may be in the direction of motion of the body
EX :1 If you are walk f a car. When the car is accelerated, direction of frictional force on the rear wheels will be in the direction of motion and on the front wheels in the opposite direction of motion
ADVANTAGES OF FRICTION :
* Friction plays an important role in our daily life. While walking friction between the ground and shoes prevent us from slipping
* Without friction motion cannot be conveyed by belts from motor to machine
* Vehicles will not come to rest even if the brakes are applied when there is no friction between tyres and the road.
* When there is no friction knots cannot be tied.
* Nails and screws do not hold the boards together without friction.
DISADVANTAGES OF FRICTION :
* Friction causes wear and tear of moving parts of the machinery.
* Friction generates heat in machine parts which damages the machinery.