Class 8 Notes: Friction CBSE NCERT

Class 8 Notes: Friction Chapter

Friction

➥ The force which opposes the motion of the objects.

Cause of Friction

Friction is caused by the irregularities on the surfaces in contact. When two surfaces try to move across each other, these irregularities interlock and resist the motion.

Types of Friction

1. Static Friction: The friction that exists between a stationary object and the surface on which it's resting. It must be overcome to start moving the object.
2. Kinetic or Sliding Friction: The friction occurring when one object slides over another.
3. Rolling Friction: The friction occurring when an object rolls over a surface. It is usually less than sliding friction.

Advantages of Friction

1. Allows us to walk without slipping.
2. Enables vehicles to move on roads.
3. Helps in writing and drawing by providing grip.
4. Enables the functioning of various mechanical parts by providing necessary grip.

Disadvantages of Friction

1. Causes wear and tear of moving parts.
2. Produces unwanted heat, leading to energy loss.
3. Reduces the efficiency of machines.

Ways of Reducing Friction

1. Using lubricants like oil and grease.
2. Polishing surfaces to make them smooth.
3. Using ball bearings to convert sliding friction to rolling friction.
4. Streamlining shapes to reduce fluid friction.

Ways of Increasing Friction

1. Making surfaces rougher.
2. Using materials with higher friction coefficients.
3. Increasing the normal force between surfaces.

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