Friction is often called a 'necessary evil'. It is 'necessary' because without it, we wouldn't be able to walk, write, or stop a car. However, it is considered an 'evil' because it causes a massive amount of problems and energy loss in our daily lives.
To reduce these disadvantages in machines, we use Lubricants (like oil or grease) and Ball Bearings, which convert sliding friction into rolling friction.
About 20% of the fuel a car uses is burned purely to overcome the internal friction of the engine.
Friction causes the physical degradation of materials over time.
Friction acts as a resisting force. When you try to move a heavy box across the floor, or when a car engine tries to turn the wheels, a significant portion of the applied energy is wasted just fighting against the friction.
When two rough surfaces rub against each other rapidly, friction generates massive amounts of heat.
Friction from the air (air drag) and water (fluid friction) slows down moving vehicles. Cars, airplanes, and ships have to be specially designed with streamlined (aerodynamic) shapes just to cut through this friction, otherwise, they would consume too much fuel.
No. In the real world, absolute zero friction is impossible. Even the smoothest surfaces have microscopic irregularities. This is why a 'perpetual motion machine' (a machine that runs forever without external energy) cannot exist.
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