Friction – Quick Notes
Definition of Friction:
- Friction is a force that opposes the motion of one object over another. It acts between the two surfaces in contact.
Types of Friction:
- Static Friction: The force of friction that acts between the two stationary surfaces.
- Sliding (Kinetic) Friction: The force of friction that acts between two surfaces when one surface slides over another.
- Rolling Friction: The friction experienced by a rolling object on a surface.
Comparison of Friction Types:
Static friction > Sliding friction > Rolling friction
Causes of Friction:
- Interlocking of surfaces due to presence of tiny hills and valleys.
- Force of adhesion between the atoms/molecules of two surfaces.
Factors Affecting Friction:
- Directly proportional to the force with which two surfaces are pressed together. For example, the weight of the body if it is placed on a horizontal surface.
- Depends on the nature of the surfaces in contact.
- Does not depend on the area of the surfaces in contact.
Advantages of Friction:
- Enables walking
- Enables movement of wheels .
- Helps in holding objects.
- Essential for braking.
- Necessary for writing with pens or chalk.
Disadvantages of Friction:
- Causes wear and tear.
- Generates heat and loss of energy.
- Reduces the efficiency of machines.
Ways to Increase Friction:
- Increasing roughness of the surface in contact.
- Using treaded tires.
- Grooved soles on shoes.
- Rough and dry surfaces.
Ways to Reduce Friction:
- Polishing surfaces.
- Applying oil or grease, lubricants.
- Using ball bearings.
- Streamlining the shape of objects.
- Sprinkling soft powder.
Drag or Fluid Friction:
- The friction between a solid and a liquid or gas.
- Depends on the speed, shape, size of the object, and nature of the fluid.