There are many forces that act on our environment. One of these is a force of friction. I remember my friend Kenneth was walking few minutes after a heavy downpour. The area was muddy. As he was walking, I saw him slipped off from the ground and fell down. This clearly explains how friction has reduced to some level. The wasn't much rough surface and that means friction has declined. There are everyday activities that explains friction.
Friction is the force which opposes two bodies in contact. For example, the bottom of my shoe and the ground are two different bodies. As I begin to walk, the bottom of my shoe get contact with the ground.
Friction depends on the rough surface. The ground being rough prevent movement of the of the bottom of shoe from slipping off the ground. Because of friction, the bottom of shoes are made to be rough in order to prevent one from slipping.
The tyre of vehicles are made rough to increase friction in order to prevent the car from skidding off the road. The vehicle could skid of the road if the roughness of the tyre is wear off and the road is made to be smooth.
This basically explains the principles of friction. The smooth surface decreases the rate of friction, but if we make the surface to be rough, friction increases.
For instance, a corn mill machine is able to grind maize due to an increase in roughness of the surface of gear and interlocking. When the rough surface of the gear is wear off, the corn mill machine isn't able to mill the corn.
A Vehicle in motion is able to stop as soon as a break is applied due to friction. Without the friction, the vehicle can't stop.
The most things that are disadvantage to friction are that it reduces the efficiency of machines. Due to the rough surface nature of friction, most frictional machines aren't able to work fast and efficient as expect. The retardation of work due to rough surfaces reduce the work outputs.
Friction wear off machine parts. For instance the gear surface of the corn mill machine wear off to a point that it needs to be sharpened. the foot of our shoes are destroyed by friction. The blade of cutlass wear off easily through continuous sharpening due to friction.
Most fluids especially liquids are very thicker which prevent substances from penetrating through. The force in liquids that prevent movement of objects through them is known as Viscosity. Many liquids are more viscous implying they don't allow objects to pass through easily and faster. An example of such liquids are grease and paints. It's very difficult for a metal ball to descent to the bottom of a grease. In the same way paints has that property. Some of the examples of less viscous substances are water, petrol and alcohol. They are very lighter and hence easily allow substances to pass through them.
That's why grease are used as lubricant to lubricate the ball bearings to prevent rusting. If grease is made to be light, it can't be used as lubricant. For paints to become less viscous, unless they are diluted with water.
