Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. It may be thought of as the opposite of "slipperiness".
Observe the surface of a table with a powerful magnifying lens. you will notice that it is rough and has very small irregularities in the form of grooves and ridges.
When one surface moves over another these grooves and ridges get caught up with each other and slow down the motion. This causes FRICTION
There are some advantages of friction some of them are mentioned here
1. It is becomes difficult to walk on a slippery road due to low friction. When we move on ice, it becomes difficult to walk due to low friction of ice.2. We can not fix nail in the wood or wall if there is no friction. It is friction which holds the nail.3. A horse can not pull a cart unless friction furnishes him a secure Foothold.
Despite the fact that the friction is very important in our daily life, it also has some disadvantages like:
1. The main disadvantage of friction is that it produces heat in various parts of machines. In this way some useful energy is wasted as heat energy.2. Due to friction we have to exert more power in machines. 3. It opposes the motion. 4. Due to friction, noise is also produced in machines.5. Due to friction, engines of automobiles consume more fuel which is a money loss.
There are some ways of minimizing friction some of them are
By polishing the surface
By streamlining(narrow in the front and broader at the back) to reduce drag (friction in fluid)
By using ball bearings or wheels – rolling friction
A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the moving parts of the bearing.
The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. It achieves this by using at least two races to contain the balls and transmit the loads through the balls. Usually one of the races is held fixed. As one of the bearing races rotates it causes the balls to rotate as well. Because the balls are rolling they have a much lower coefficient of friction than if two flat surfaces were rotating on each other.
There are some ways of increasing friction some of them are
Sand and gravel are strewn on slippery ground during the rainy season to increase friction. It is then easier to walk on the ground.
spikes are provided in the soles of shoes used by players and athletes to increase
Friction so that they get a firm grip on the ground.
Gymnasts apply a coarse substance on their hands to improve their grip.
Tyres have designs and patterns with grooves on the surface to increase friction with the road . This prevents slipping of the tyres on a wet road
Tyres of cars
Sand and gravel
Spikes on soles of shoes