Method to Change Friction

Friction is a necessary evil. Let us now discuss the ways of reducing friction.

1. Making surfaces smooth by using lubricant:-

Moving parts of machines are therefore, made very smooth. For this, the moving parts are covered with oil or grease. By the use of a suitable lubricant, like oil (for light machinery) or grease (for heavy machinery) friction can be reduced. Lubricants may be in solid, liquid or gaseous forms. When a lubricant is used between two moving surfaces its particles get into the uneven parts of the surfaces and make a thin layer of their own between them. As a result, the motion actually occurs between the layers of lubricating material which are relatively smoother. This is helpful because fluid friction is less than solid friction.

2. If you leave your bicycle unused for a month and then ride it, it needs great effort from you. When you put some machine oil on the chain and sprocket-wheel, the bicycle runs with much less effort. This is because, the friction opposes motion and hence you have to put more effort to move it. The machine oil reduces friction and the bicycle runs more easily.

3. By polishing:-

The surfaces are highly polished, to eliminate the irregularities. This makes the surfaces smooth and reduces friction to a great extent.

4. By using fine powders:

Talcum powder is used as a lubricant. When we sprinkle powder on a carrom board, the depressions on the surface of the board and the coins of carrom get filled with the powder. This makes the surface smoother and reduces friction between the board, the striker and the coins of the carrom.

5. Graphite being very soft solid which can be ground to a very fine state. It is then used as a lubricant in those parts of machines, where it is difficult to apply oil. It reduces friction by filling up unevenness between the surfaces.

6. By streamlining:-

Friction due to air (air resistance) or water is reduced by using streamlined shapes in aeroplanes or ships. A streamlined shape is narrow in front and broader at the back. All birds have streamlined bodies to ensure minimum friction as they fly through the air. In the same way, ships, boats and fish have streamlined bodies, so that they can move easily in water.

7. By using soap solutions:

Soap solutions are used in cutting and grinding machines to reduce friction.

8. Using ball bearings:

Ball bearings are used in machines to reduce friction. These in machines to reduce friction. These are tiny steel balls often placed between moving parts of machines. You might have seen them fitted in the wheels of a bicycle. They reduce friction and save a lot of energy.

9. Using wheels or by converting sliding friction into rolling friction:-

Use of wheels between surfaces moving over each other reduces friction. We know that rolling friction is very less than the sliding friction between the two surfaces. Due to this reason, many heavy objects, such as suitcases, travelling bags are provided with small wheels, called as rollers. The rollers reduce friction and help in moving heavy objects easily from one place to another.

Methods of increasing friction :-

1. By making the moving surfaces rough: Tyres of vehicles have designed with grooves on the surface to increase friction. A large friction provides a better grip to vehicles on the road arid prevents them from skidding.

2. By increasing roughness of surfaces: The surface of a matchbox and the head of. the matchstick are deliberately made rough to increase friction.

3. During rains the ground become slippery. So, sand and gravels are spread on grounds to increase friction.

4. You must have seen the spikes in the soles of shoes used by players and athletes. This is done only to increase friction.

Sample Questions

(More Questions for each concept available in Login)

Question : 1

You must have seen the spikes in the soles of shoes used by players and athletes. This is done to ____________
A. Increase friction	B. Decrease Friction	C. No effect on friction	D. None of the above
Right Option : A
View Explanation

Question : 2

When two surfaces are coated with lubricant, then they can easily__________________ .
A. Stick to each other
B. Slide upon each other
C. Roll upon each other
D. None of these
Right Option : B
View Explanation

Question : 3

Which of the following method is used to avoid friction ?
A. Making surface smooth	B. Polishing	C. Soap solution	D. All of the above
Right Option : D
View Explanation