not talking - only rides,
Because - sleet,
But great fall!
Why did no one is happy?
so naive nursery rhyme at first sight - and how much it contains, if you look at it from a physical point of view!After all, there lies a system contradictory attitude to the proverbial friction force.This constant battle, which compete with each other two concepts - the harm and benefit of the friction force will never be a winner.After all, what one person is comfortable and beneficial to another is often quite the opposite - it is bad, as in this poem.
Remember the story of Nikolay Nosov about the icy hill, which was built in the courtyard of the guys?And when they went to lunch, came the one that did not take part in the construction.He tried to get on it, but only hurt himself, but to climb and could not.And guess baby sprinkle the ice with sand - it has become very convenient to climb to the very top, even on ice!Thus, strengthening with sand friction between the ice and slippery soles, the boy realized that the use of friction allows to overcome obstacles.
But after lunch the kids went out with Ice-boats to their hearts' content to roll on its hill.An there it was: do not go sleigh on the sand!For them, this situation turned around the other side, showing the damage to the friction.
Such cases we have seen in the winter when the boys rolled icy track and carry with them a running start, breaking away in a matter of minutes!And after hobble elderly, slips on powdered snow Nakata and fall, breaking the arms and legs.Here it is again illustrative examples where the same case, the neighborhood and the harm and benefit of friction.
It is to reduce the friction forces skiers smeared his skis special ointments to increase the speed of the motion.Rollers, which are engaged skaters or skaters, periodically watered and clean - also in order to reduce friction.A pedestrian walkway, on the contrary, sand or ash to one they did not fall.Some inventors, innovators come up with even stick to the soles of shoes and winter boots pieces of sandpaper just to increase friction.
The same thing happens with the wheels of cars.It is no secret that with the onset of winter, drivers "shoes" of their iron horses in a special "winter tires".Otherwise no useful friction force increases braking distances, there is a skid when the machine turns, it yuzit, and often the driver copes with bad management.And what end accident, everyone knows himself.
Something we are all about winter, but about the ice, but about the fall.And there are other moments in the everyday life, which can be clearly seen as competing with each other harm and use the force of friction?Of course have!They're everywhere.Even in this room with you.
For example, a huge and heavy wardrobe.It is worth himself rooted to the spot, and does not move.And if suddenly disappeared frictional force, then what would happen?And I went to this whopper from the easy push of the room!And yet known, could we manage to dodge it.Good frictional force, useful!
But my mother decided to rearrange the furniture.And you need to move this notorious shkafische to another wall.One - two, heave!Three - four podnapryaglis!Just everything is useless: the heavier the object, the stronger hold on to it the force of friction.Horrible, nasty silischa!
Again they compete with each other - and the use of harmful friction.And it does not need any competition!You just have to know well the laws of physics and be able to extract this knowledge from practical use.I do not need at the moment the force of friction?So, it should be reduced: make mating surface more smooth, slippery.Someone advised to spread the floor of soap or oil, someone puts a heavy object feet wet rag.And now - one - two - and voila!It moved fairly easily to places such utter edifice.
friction force is constantly accompanies us throughout life, as well as the force of gravity.Somewhere it creates inconvenience us, but somewhere without it can not do.But be that as it may, it exists, and our task - to learn how to use the laws of physics, so that our lives become more convenient and comfortable.
