What is Friction?
Since our childhood, all of us have been hearing to the term ‘friction’ that it reduces the speed of vehicles and also wears out the parts of machines. It is a fact. Friction leads to resistance in motion which acts in reverse direction of motion.
Your bicycle stops all of a sudden when you put a brake on it, since this way, you raise the friction between the road and wheels. Pushing a box on a cemented surface is more difficult than on a smooth surface. It is because cemented surface leads to more friction owing to its irregular surface. In contrast, pushing the same box on a glass table is very easy. It is because it contains a very smooth surface which results in lower friction.
Types of Friction
Friction is of 3 types. These are static friction, kinetic friction, and fluid friction. These three types of friction perform on an object in a different way. Let us see how:
As the name suggests, static friction takes place between the objects which are in contact with each other but not in motion. Hence, suppose you put a heavy box on a table, will it involve the static friction? The answer to this question is ‘NO’.
Then, when does static friction in fact take place? Static friction takes place only between two static objects that are stationary even when the force is applied on those objects. For instance, when you place a box on the table, it will never undergo static friction until you use a force to slide it but it still does not move. In this case, it is undergoing the static friction. However, when you push the box with more force, the box will start moving. At this time, the static friction will be changed to kinetic friction.
Let us start learning about the kinetic friction with an example. What will happen if you are riding a bicycle so fast, and abruptly stop paddling? You will observe that the bicycle starts slowing down before coming to an absolute stop. This is what we call the kinetic friction.
When one object is moving on another, both will undergo kinetic friction. Kinetic friction as a rule takes place between the moving objects (in our case, the road and the wheels of bicycles). In general, because of the motion of the objects, kinetic friction is less than the static friction.
Kinetic friction is further categorised into two kinds:
Sliding friction: The two objects will feel the sliding friction when they slide on each other. Rubbing your hands and pushing a box are the two examples of sliding friction.
Rolling friction: The two objects will undergo rolling friction when one object rolls on the other, or when they are rolling on each other. Rolling friction is less than the sliding friction; therefore, it is easier to push a weight on wheels than to slide it. The bicycle you ride undergoes rolling friction.
Though solids experience two types of friction to an object, there is one more type of friction as well that is offered by the fluids, e.g., liquids and gases. Go through the example given below to get familiar with the concept:
When you drop a coin in an oily liquid, i.e., cooking oil, what will happen? The coin will go down gradually to the bottom. This happens due to the fluid friction, because the oil is resisting the motion of the coin downward. Fluid friction rises with two factors—the velocity of the object and the viscosity (thickness) of the fluid. If you take honey instead of cooking oil, it will offer more friction to the coin. It is because honey is more viscous than cooking oil.
How is Friction Important in Our Daily Life?
Friction enables us to walk on the ground. Else, we would slide away.
In winters, we warm your hands by rubbing them together.
We stop vehicles quickly by applying brakes on them.
It helps us hold a pen or anything firmly. In the absence of friction, the object held by us would easily slip out from our hand.
Why is Friction Avoided?
Friction leads to wears in the machine parts. Hence, we lubricate them to decrease friction.
In order to diminish friction, the joints in our body are well lubricated.
Lower fluid friction can escalate the mileage of our vehicles. We spend the most of our fuel in combating friction beyond the speed of 80 km/h.