Chapters

Friction

Friction is the force that opposes the motion of an object. When we push an object with only a small amount of force, it does not move at all. It means that the surface on which the object is resting applies some force on the object and the force is acting in a direction opposite to the force of our push this force is knwon as Friction.

eg: A ball moving on the ground slows down or stops due to the friction between the ball and ground.

Cause of Friction

Whenever we see the surface of any object through microscope it always have some rough patches, even though if it looks like smooth with naked eyes. When the rough patches of two surfaces moves over each other they get locked. The interlocking of two surfaces opposes the motion of one body over another and gives rise to frictional force.

Laws of Friction

The four important laws of friction are as follows:

  1. Friction opposes the motion
  2. Friction is independent of the area of contact between the two surfaces
  3. Friction depends on the nature of the two surfaces in contact. In other words, firction depends on the kind of materials, smoothness and degree of lubrication.
  4. Fractional force is directly proportional to the weight of the body which tends to move. This is why it is difficult to move heavier objects

 

Types of Friction

Maily the friction is of three types:

  1. Static Friction: It is the friction exerted on a object at rest. Station friction is also known as limiting friction
  2. Sliding Friction: Sliding friction is slightly less then the static friction. It is exerted when an object slides over a surface. Sliding friction is also known as dynamic friction or kinetic friction.
  3. Rolling Friction: It is the friction exerted when an object rolls over a surgace.Rolling friction is always less then the sliding friction and static friction.

 

Methods of Reducing Friction

Friction is caused due to the roughness of surface. Any process by which we can make the two surfaces smooth will reduce the fiction. Some commonly used methods for reducing friction are:

  1. By polishing
  2. By applying lubricants(oil or greese)
  3. By using ball-bearings
  4. By using rolars and wheels

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