FRICTION

FRICTION
When a solid is in contact with another, the roughness of their surface prevents them from sliding freely over one another. Such action is brought about by the effect of friction.
Friction is defined as a force, which acts at the surface of separation between two objects in contact and tends to oppose the motion of one over the other. Frictional forces act tangential to the surface of separation between two bodies in contact. Friction is a force of opposition.

TYPES OF FRICTION
There are two major types of friction namely:
a.            Static friction 
b.            Kinetic or dynamic friction 
Static friction: This is the maximum force that must be overcome before a body can just start to move over another.
Kinetic or dynamic friction: This is the force that must be overcome so that a body can move with uniform speed over another body.

Result of experiments lead to the following laws of solid friction 
1.           Friction opposes relative motion between two surfaces in contact 
2.         The force of friction increases to the same extent as the force which tends to start the motion 
3.            Frictional force depends on the nature of the two surfaces in contact
4.            It is independent of the area of the surfaces in contact
5.      It varies directly with the normal force pressing the surface together i.e. it is proportional to the normal reaction R.
Advantages of friction
1.            Without friction, it would be impossible to walk or stop walking after getting started 
2.            Friction enables the automobile tyres to make a firm grip with the roadway, thus aiding their movement
3.            Friction enables the brakes to stop the car, and the locomotive to pull the train 
Disadvantages of friction 
1.            Friction leads to much wear and tear on the moving parts of machines
2.            Friction causes the heating of engines
Method of Reducing Friction 
1.            The use of lubricants like oil, grease, air and graphite.
2.            The use of ball or roller bearings and 
3.            The stream lining of body shapes of moving objects 
    

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