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FRICTION FORCE
Friction force is the type of force which exist between two surfaces in contact and tries to oppose their relative motion. The force start to exist when two surfaces want to move over one another.
Friction force act in a perpendicular direction to the two surfaces in contact. It come to existence when one surface tries to move over the other surface.
Types of friction force:
1.Static or Limiting Frictional Force:
This is the maximum amount of friction force that must be overcomed before an object can just start to move over another object.
2. Kinetic or dynamic friction force :
This is the friction force that must be overcomed so that a moving object can continue to move with constant speed over another object.
Note that coefficient of static friction is always greater than coefficient of dynamic friction.
Coefficient of Static Friction Force > Coefficient of Dynamic Friction Force
Laws Of Solid Friction
The laws of solid friction states that :
1. Friction force exist between two surfaces in contact
- Friction force opposes the relative motion of the two surfaces in contact
- Friction force is proportional to normal reaction
- Friction force does not depend on the area of the surfaces in contact
- Friction force act in a direction that is opposite to that of motion
- Friction force depends on the nature of the two surfaces in contact
Relationship Between Friction Force, Normal Reaction and Coefficient Of Friction:
From the definition,
Friction force is directly proportional to normal reaction
Friction force & normal reaction
Friction force = µ x normal reaction,
µ = friction force / normal reaction
Advantages Of Friction Force:
1. Friction force makes movement possible
2. Friction make car brake to function
3.Friction is used in grinding stone
4.Friction enable screws and nail to remain in place after screwed or nailed
5.Friction is used in belt and pulley system
Disadvantages Of Friction Force:
1.Friction force reduce efficiency of machine
2.Friction force generate heat
3.Friction causes wear and tear of machine parts
4.Friction reduces motion
5.Friction causes wastage of capital
Method Of Reducing Friction:
1. Streamlining of object:
Streamlining of objects means to shape an object with a pointed end. Streamlining helps to reduces friction force between an object and air or water molecules.
2. Lubrication:
Lubrication of surfaces in contact helps to separate the two contact surfaces and therefore eliminate or reduces friction force between the two surfaces. The lubricant form a thin film between the surfaces and therefore eliminate friction force between the surfaces.
3 Using ball bearing or rollers:
Ball bearing between surfaces separate then surfaces and therefore eliminate friction force between the surfaces.
4. Publishing of surfaces:
Publishing of surfaces helps to make the surfaces smooth which in turn eliminate friction force between the surfaces.
4. Introducing air between the surfaces:
Introducing air between the surfaces help to separate the surfaces and therefore reduces Friction force between surfaces