The physics of conflict, the ‘necessary evil’ that affects everyday life

The good old game of carrom has really stood the test of time. Set up a board and people will flock to it while practicing their finger muscles. You may not have noticed but the game often begins with an underappreciated event: a bit of magic powder spread over the board that somehow energizes the floating coins, helping them slide smoothly with just a slight push.

What did that little bit of flour do?

To fix the friction

Friction is an invisible force that surrounds us and slows us down every time we move. Isaac Newton told us long ago that when something is in motion, it will continue to do so unless it is stopped. So why doesn’t the car continue to move when it is pushed? That way we could just get somewhere without spending any money on fuel – and we wouldn’t have to worry about its price going up or down.

The reason is conflict. Even if we make the roads as smooth as possible, there will always be some friction that will slow the car down. The invisible air causes collisions between airplanes and birds. The trickiest part of our rockets is the phase when they leave the earth’s atmosphere. Air friction creates a lot of heat – the same heat you generate when you rub your hands together on a cold day. In outer space, there is no air and spaceships travel much more easily, often much longer distances with a single push.

Where does this conflict come from?

Any surface – such as a carrom board or your desk – may appear to be smooth and level, but it is not. In fact, there is no perfect match in the universe. If you look at any surface closely, you will notice small spots: basically a few bumps and some dips, like a camel’s back.

The surfaces of the carrom board and the carrom grain also have bumps and dips. When a coin tries to move across the board, the bumps and dips on both sides will hit each other, slowing the coin down. This is an argument in play. Friction can occur if there are substances sticking to both surfaces, such as greasy dirt. In short, friction occurs due to forces or interactions between two surfaces.

Think of coin carrom like a car on the road. If the road is smooth, the car will move easily. But if there are bumps and dips, the tires will have difficulty moving, and the car will slow down. The rougher the surface, the more friction there is.

We repair the broken road by filling the holes. Similarly, that little bit of flour fills all the little invisible holes in your carrom board, and the coins flow easily.

Dosa pan and wind chimes

You may be wondering: isn’t there an easy way to remove all the fuss? Well, people have found amazing ways to do this. The simple version is something you’ve been doing at home, and for a long time. If you ever make a dosa or something they kissed and moaned, you may have splashed water on the hot pan before or after. The water drops move across the pan as if they were not competing with each other. This usually checks if the pan is hot enough. But why does the water not stick to the pan?

This is because as soon as the water droplets hit the hot surface, a thin layer of vapor forms beneath them. So the water drops really float in the pan. As the surfaces are no longer in contact, they have very little friction, allowing the droplets to slide.

In one of the first physics courses at IIT Kanpur, where I teach, new students did experiments to verify Newton’s laws, like the one I mentioned earlier. But Newton’s laws are only true when there is no friction. So we have to make things go without friction first.

Another clever way is to do an experiment where the object is made to move wind track. A certain amount of air is continuously pumped from inside the trains using powerful air blowers. If the object is not too heavy, it can ‘float’ above the track by staying in the air, and move as if there were no friction. As a result, students can now test Newton’s laws for themselves.

In fact, high-speed trains using the principle of magnetic attraction do the same thing. Here, the entire passenger train floats in a strong magnetic field created by the tracks. So there are less collisions and trains can run at higher speeds.

The problem with electrons

Just as cars have difficulty traveling on broken roads, electrons find it difficult to travel through metal, such as copper wire. This is why we pay our electricity bills: so that someone somewhere can continuously apply a certain voltage to the wires, and electrons pass through them and come to our homes.

What can stabilize electrons within a material? Just like roads have potholes, everything around us has them dirt. For example, any copper wire will contain traces of other metals, such as zinc or aluminum. The atoms of these metals create ‘friction’ for the electrons and slow them down as they pass. So if we can remove this friction, we will be able to get the wire to conduct a larger current without applying any voltage.

You might even think that if we can remove all the dirt from something, we can avoid paying the electricity bills. Unfortunately, this is not possible. Although Newton’s laws are sufficient to explain how carrom balls move on a board or cars move on a highway, they are not sufficient to explain electrons.

Here, the laws of quantum mechanics come into play. A careful study of quantum mechanics and its application to materials tells us that there is another way to remove the friction of electrons – with the help of something called superconductivity. If you are more interested in learning about superconductors and their interesting properties, a physics course may be worth considering.

So the next time you curse rising fuel prices, remember you’re not alone. The real problem is collisions – which cars, carrom coins, and electrons struggle with.

The author is an assistant professor at IIT Kanpur.