Friction can occur as a result of a solid material sliding over another solid surface which gives rise to resistance in motion. This resistance is called Friction. Friction is always required in engineering. For example, a car must maintain friction between its tyres and the road to be able to move forward or backward. It is also required to bring it to a stop by applying the brakes.
Friction between the brake pad and the wheel drum must be created before the car can be put to a stop. Friction is required in most of the things we do. Examples are:
- To Run: To be able to run, friction is required between your shoe and the ground; otherwise, you will not be able to run but slide about.
- To Sit : To sit down on a chair requires friction between your buttocks and the chair so that you don’t slip off the chair.
It is stated that:
- The rougher the surfaces rubbing against each other,the more the friction.
- The smoother the surfaces rubbing against each other,the less the friction.
To create or increase friction, the rubbing surfaces should be made rougher; and to reduce friction, the rubbing surfaces should be made smoother. The brake system of a car operates on this principle. This is why when you go to buy tyres, you should buy those with good threads so as to give you good friction between the car tyre and the road.
In Technology, the effects of friction are used in the following examples:
- When you strike a match, it is the friction between the matchstick and the match box that enables the match to light up.
- In sharpening a pencil, friction is required between the sharpener blade and the pencil for sharpening to take place.
- In sharpening a knife with a file, friction is also employed. The knife wears under friction created by the rough surfaces of the file, thereby becoming sharpened.
HOW TO CREATE FRICTION
Clean and dry the palms together vigorously for about five seconds. You will notice that your palms have become warm. This is due to friction which is caused by the resistance to motion of one palm relative to the other.
HOW TO REDUCE FRICTION
Rub your fingers on a plain metal or glass, first, without oil then with some oil on your fingers. Certainly it was when the oil was applied the friction reduced.
DISADVANTAGES OF FRICTION
- When one solid part of a machine rubs constantly against another solid part, there is always heat created as a result of friction. Friction leads to wear and tear, which may lead to damage on the weaker part or even on both.
- When a tool is sharpened on the grinding wheel, it gets hot. This is caused by friction and if not cooled, can lead to the burning out of the cutting edge of the tool.
- In drilling operations, the metal chips rub over the lips of the drill and heat is caused as a result of friction between the chips and the lips of the tool. This heat may weaken the drill. A cutting fluid is therefore used to take the heat away from the lips of the drill and to wash away the chips. The drill will last longer and the hole will be smoother.
A lubricant is an oily substance; examples are: grease,oil or other substances that can make surfaces smooth and slippery, thereby reducing heat, wear, friction and vibration caused when two or more surfaces rub together. To lubricate means to make a surface smooth and slippery by the application of a lubricant such as oil.