Harm and benefit of frictional force

Do not go - just going,

Because - ice,

But it falls perfectly well!

Why is no one happy?

Such a naive nursery rhyme at first glance - and how much it contains if you look at it from a physical point of view! It is in it that a system of contradictory attitude to the notorious force of friction is concluded. This constant battle, where two concepts compete with each other - the harm and benefit of friction, will never have a winner. After all, the fact that one person is convenient and profitable, another often quite the opposite, is bad, as in this poem.

Do you remember Nicholas Nosov's story about the ice hill that the children built in the yard? And when they all went to dinner, someone came out who did not participate in the construction. He tried to climb on it, but only hurt himself, but could not get away. And the kid guessed to sprinkle ice with sand - it became very convenient to climb to the very top even on the ice! So, having strengthened with the help of sand the force of friction between the slippery ice and the sole, the boy realized that the use of friction makes it possible to overcome obstacles.

But after lunch, the children came out with cold feet, in order to roll on their hill. And it was not there: they did not go sledge on the sand! For them, this situation turned the other side, showing the damage of friction.

We see such cases in the winter, when the boys roll out the ice tracks and rush along, overcoming the distance in minutes! And then the older people hobble, slip on the snow-fed rocks and fall, breaking their arms and legs. Here you again have clear examples, where in the same case, both harm and the use of frictional power are side by side.

It is to reduce the friction force, skiers lubricate their skis with special ointments to increase speed when driving. Skating rinks, which are engaged in skaters or skaters, periodically watered and cleaned - also to reduce the frictional force. And the pedestrian paths, on the contrary, are sprinkled with sand or ash, so that no one falls on them. Some inventors-innovators have come up with even glued to the soles of winter boots and boots pieces of sandpaper just to increase the frictional force.

The same happens with the wheels of cars. It's not a secret that with the onset of winter, drivers "shoe" their iron horses into special "winter tires". Otherwise, without a useful frictional force, the braking distance will increase , the car will roll when cornering, it juts, and often the driver does poorly handling. And how do crashes end, everyone knows and himself.

Something we all about the winter, but about the ice, but about the fall. Are there other moments in everyday life, where you can clearly see how the harm and benefit of frictional power compete among themselves? Of course have! They are everywhere. Even in our room with you.

Here, for example, is a huge and heavy wardrobe. It is worth it, as if stumped, and does not move. And if the force of friction suddenly disappeared, what could have happened then? And this giant would have gone from the slightest push in the room! And still it is not known, we could manage to dodge it. Good friction force, useful!

But my mother decided to rearrange the furniture. And you need to move this notorious cabinet to another wall. Once or twice, they took it! Three - four, have been strained! Only everything turns out to be useless: the heavier the object, the stronger is the friction force. Terrible, nasty power!

Again they compete with each other - the harm and benefit of the force of friction. And do not need any rivalry! You just need to know the physical laws well and be able to extract practical benefits from this knowledge. Do not need friction force at the moment? So, it should be reduced: make the contacting surfaces smoother, slippery. Someone for this advises to spread the floor with soap or oil, someone puts a wet rag under the legs of a heavy object. And now - once or twice - and it's ready! They moved it quite easily from place to place.

The force of friction constantly accompanies us throughout life, just like gravity. Somewhere it creates us an inconvenience, and somewhere without it we can not do. But anyway, it exists, and our task is to learn how to use physical laws so that our life becomes more comfortable and comfortable.