Ways of Increasing Friction and Reducing Friction
Methods of Reducing friction
Wear and tear due to friction depends on two factors: the roughness of the two surfaces in contact and the amount of time the two surfaces rub against each other. Wear and tear of an object is not desirable as it reduces its life. This is more so in case of moving parts in automobiles and machinery. Therefore, efforts are made to reduce friction between moving parts.
Friction between moving parts is usually reduced by introducing a substance between the moving surfaces. This process is called lubrication. The substance introduced is called a lubricant. Common lubricants are oil and grease.
Ball bearings are also used to reduce friction. Ball bearings change sliding friction to rolling friction. This is a very useful thing to do since rolling friction is much smaller than sliding friction. Ball bearings are used in most mechanical structures which have moving parts. Small metal balls made of stainless steel, brass, ceramic, etc., are placed between moving surfaces (the surfaces . can be flat or cylindrical) to reduce friction.
Other than friction between solid parts, there can also be friction due to fluids (e.g., air and water). The force of friction due to air and water (and other fluids) is called fluid friction. When cars and aeroplanes move at very high speeds, their motion is opposed by friction offered by the air molecules surrounding them. The friction of air produces what is called drag, which opposes the motion of the vehicle. The same applies to ships and boats. To reduce drag, automobiles, ships, and aeroplanes are given a special shape, called a streamlined shape. An automobile with a streamlined body experiences minimum resistance when travelling through air. Even sea creatures like fish and shark have streamlined bodies, which makes it easier for them to move with great speeds in water.
Frictional force can be reduced in the following ways
- Use of lubricants: In machines, friction can be reduced by applying lubricants between the contact surfaces to fill the fine pores or depressions in the surfaces and make them smooth thereby reducing friction.
- Polishing : unevenness of the surfaces can be reduced by polishing, thereby reducing the friction.
- Use of ball bearings: In rotating machines, shafts are mounted on ball bearings. By doing so, rolling friction occurs lesser than sliding friction, thereby reducing the friction.
- By streamlining: Air friction is reduced by designing streamlined bodies of cars or aeroplanes. Similarly, if the bodies of boats and ships are streamlined, friction of water can be reduced.
Methods of Increasing Friction
There are two methods of increasing friction: one is by making the surfaces rough and the other by increasing the mass of the object that is moving.
For example, the tyres of vehicles have treads (these are the ‘designs’ that you can see on the tyre surface), which increase the friction between the tyre and the road. Similarly, the soles of shoes have grooves, in order to increase friction. Gymnasts often apply a coarse material on their hands to get a better grip by increasing friction.
Activity
Aim: To show that greater friction causes increased wear and tear.
Materials needed: A new eraser, a piece of paper from your notebook, a piece of cardboard, and sandpaper.
Method: Use the eraser to rub on the different surfaces mentioned above. Each time, make a note of the amount of wear and tear on the eraser.
Observation: You will see that the rougher the surface, the greater the wear and tear.
Conclusion: Greater friction causes increased wear and tear.