Friction is one of the most useful and one of the most troubles causing phenomenon in physics. In this article we will understand why. Firstly, let us analyze the factors that cause friction and then venture into the pros and cons of it. Thousands of years ago humankind discovered that rubbing two rocks against each other can produce a spark which in turn can produce fire. Fire is one of the most important inventions of mankind. We have survived for millennia because we could make and use fire.
What we then realized is that the two rough surfaces when rubbed against each other resist the motion causing heat to be produced. It was the inherent nature which is the roughness in the rocks that caused it. It can be visualized from the fact that when the rocks rub against each other the surfaces do not like it or resist it. That is because the contours on the surfaces lock against each other and it requires energy to break those locks. This is a simple way to explain friction.
We have recently realized that these interlocking of surfaces is a very complex electromagnetic phenomenon that happens at the atomic scale on the surfaces which is why even seemingly smooth surfaces like ice or a sheet of metal contain some amount of friction or a resistive force against something moving against it. Friction thus exists everywhere and during our Physics tuition classes, we often take it into account in the topics of Kinematics, Forces and Dynamics. We can move, commute, talk, eat, breathe, and stay alive because of friction.
On the other hand, we are continuously battling the energy lost due to friction. For example, from the times we were using wooden wheels on a cart to the times we are now using magnetic levitation trains, we are trying to minimize the losses in energy due to friction. Friction takes up almost one third of the energy input in an automobile.
Overcoming one third of the energy is a lot of fuel being used to overcome friction. Cutting edge research in automobile industry has reducing these losses in energy and optimizing fuel consumption as one of their top priorities. But that cannot be all, there has to be so many other uses of friction that we may at times look away from the cons.
For example, the friction between two liquid surfaces called viscosity and the friction between a liquid surface and a solid surface called ‘lubrication friction’ are two useful forms of friction that helps us mitigate the losses due to friction in automobiles. The braking of a car would be impossible if not for friction, not only the frictional forces between the tires and the road but also the frictional forces that act within the drum or the disc brakes and the wheel. Controlled friction helps the driver shift gears in an automobile with ease and has better control on the automobile.
Advances in atomic force microscopy have also enabled us to get a better picture of friction and how to use it for our advantage. To conclude, we can say friction is a very interesting paradox.