Not going - just going
Because it is icy
But it falls perfectly!
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! Indeed, it is in him that the system of a contradictory attitude to the notorious friction force is enclosed. This constant battle, where two concepts compete with each other - harm and the benefits of friction, will never have a winner. After all, what is convenient and profitable for one person, often quite the other way around, is just the opposite - bad, as in this poem.
Remember the story of Nikolai Nosov about the ice slide that the guys built in the yard? And when they all went to dinner, the one who did not participate in the construction came out. He tried to climb onto it, but only hurt himself, but he could not climb. And the kid guessed to sprinkle ice on the sand - it became very convenient to climb to the very top, even on ice! So, having strengthened the force of friction between the slippery ice and the sole with sand, the boy realized that the use of friction allows him to overcome obstacles.
But after lunch, the kids came out with ice cubs to roll on their own hill. But it wasn’t there: sledges on the sand do not ride! For them, this situation turned the other side, showing the harm of friction.
We observe similar cases in the winter, when the boys roll out ice paths and rush along them, covering the distance in a matter of minutes! And then the elderly waddle along, slip on the snow-covered coasts and fall, breaking their arms and legs. Here are again illustrative examples for you, where in the same case harm and the benefits of friction are combined.
It is to reduce the friction force that skiers lubricate their skis with special ointments to increase speed when moving. The skating rinks used by skaters or skaters are periodically watered and cleaned - also to reduce friction. And the pedestrian paths, on the contrary, are sprinkled with sand or ash so that no one falls on them. Some inventors, rationalizers even came up with sticking pieces of sandpaper to the soles of winter boots and boots just to increase the friction force.
The same thing happens with the wheels of cars. It is no secret that with the onset of winter, drivers “put on” their iron horses in a special “winter rubber”. Otherwise, without the useful friction force, the braking distance increases , the car skids when cornering, it runs, and often the driver does poor control. And what the accident ends with, everyone knows himself.
Something we are all about winter, but about the ice, but about the fall. Are there any other moments in everyday life where you can clearly see how harm and the benefits of friction compete with each other? Of course have! They are everywhere. Even in our room.
For example, a huge and heavy wardrobe. It stands itself rooted to the spot and does not move. And if the friction force suddenly disappeared, then what could happen? And this giant would go from the lightest push around the room! And it is still unknown if we could have time to dodge it. Good friction force, useful!
But then mom decided to rearrange the furniture. And you need to move this notorious cabinet to another wall. One - two, they took it! Three - four, strenuous! Only everything turns out to be useless: the heavier the object, the stronger the friction force holds on to it. Awful, nasty power!
Again they compete with each other - the harm and benefits of friction. And no rivalry is needed! You just need to know the physical laws well and be able to derive practical benefits from this knowledge. Do you need friction force at the moment? Therefore, it should be reduced: to make the contacting surfaces more smooth, slippery. Someone for this advises to smear the floor with soap or oil, someone puts a wet rag under the legs of a heavy object. And now - one - two - and you're done! They moved quite a bit such a colossus from a place.
The force of friction constantly accompanies us throughout life, just like gravity. Somewhere it creates us inconvenience, and somewhere without it can not do. But be that as it may, it exists, and our task is to learn how to use physical laws so that our life becomes more convenient and comfortable.