Have you ever thought about a question:
A boeing 747 full of passengers and fuel, with a take-off weight of nearly 400 tons, equal to over 300 cars stacked together. How can such a big thing be so stable that it can fly at a height of 10,000 metres
The first reaction of a lot of people is that the wings produce lifts because of organic wings。
But one more thing: how does the wings produce the lift
Most people are stuck。
Today's article makes it perfectly clear, in the most common words, why a plane can fly. You'll find it in four words。
First, to break a century-old “wrong answer”
The most widespread explanation of why a plane can fly is as follows:
“the upper wing is arc-shaped and the lower surface is flat. Air flows through the surface longer and faster, based onBernoulian doctrineWhen the pressure is small, the above surface pressure is low and the lower surface pressure is high, the plane gets up."
That makes sense, even in many textbooks。
But it is incomplete and even misleading。
Why? Because of the low pressure on the upper and lower surfaces of the wings alone, a few hundred tons of aircraft cannot be held up. Moreover, many of the wings of modern fighter planes are symmetrical, with the same upper and lower surface shapes that can fly。
Where does the real lift come from
The answer is four words: push the air back。
Ii. The third law of newton: the underlying causes of aircraft flight
Remember newton's third law of high school physics
The force and the reaction are equal in size and direction。
You push the wall with your hand. The wall pushes you. You kick back, the water pushes you forward。
The same goes for planes。
When the wings move in the air, a large amount of air is pushed backwards. According to newton's third law, the pushed air will give the wing an upward reaction。
This upward force, that's the lift。
So the aircraft is able to fly, essentially not because it “sucks up”, but because it “pulls down” - the wings kick the air down and the air lifts the aircraft up。
You can imagine: you're standing on a skateboard and you're throwing a heavy ball back, and you're gonna find yourself slipping out. The plane is the ball thrower, the air is the ball thrown out。
How does the wings actually “push the air”
This involves the shape and angle of the wing。
First, the wing has an angle。
While flying, the wing is not entirely horizontal, but a slightly upward angle is called the “biding”。
With an accelerator, the wing is like a tablet tilted into the air, which naturally presses down。
Second, the wing has a bend。
The upper surface of most of the wings is condensed and the lower surface is relatively flat. This shape is called wings。
When the air flow is out of date, the curved shape of the wing causes the air to turn downwards when it leaves the rear edge of the wing. The shift in direction of the air means that the wing gives the air a force down, and the air naturally gives the wing an upward reaction。
Third, the kanda effect。
The fluid has a characteristic: it flows around the bending surface. When the air flows through the upper surface of the wing, it turns downward along a radians and pushs the air further down。
So, the essence of the wing is to turn the air from the front into a downstream。
The more the air is pushed, the greater the lift。
Is that bernouli wrong
That's right, but it's a "column" and not a "principal."。
The benuli doctrine does exist and the air pressure on the surface of the wing is actually lower than the lower surface, which does contribute to some of the lifting。
But modernAerodynamicsStudies have shown that most of the lifting is from newton's third law, the downward shift of wings to air。
The bernouli effect is more like a "bringing of flowers" than a "blowing of carbon in snow."。
So next time someone asks you why the plane can fly, you can say with confidence:
“because the wings push the air down, the air lifts the aircraft up. Newton's third law, simple and rough."
V. Air flating. What do you need
It is not enough to lift a plane, and two conditions are required for it to really fly:
First, enough speed。
The size and the speed of the lift are proportionally proportional. The faster, the greater the lift. That is why before a plane takes off, it has to slip faster on the runway — not enough speed, not enough lift and not enough head。
Second, enough push。
The role of the engine is to provide the push forward and speed up the aircraft. The speed's up, the lift's coming。
So here's the flight logic chain:
The engine generates push speeds and speeds the air through the wings and pushs the air down the wings and lifts the wings up and the plane takes off。
One round, one round。
Summary
The plane can fly, not by magic, but by physics。
The core says, "the wings push the air down and the air lifts the aircraft up."。
This is the perfect application of newton's third law。
Bernouli's principle is a contribution, but not a lead. The real character is the law of physics that you've learned in high school。
It is sometimes the case that science, the most simple principle, can explain the most amazing phenomena。
Next time you fly, you can lean over the window, look at the wings and think:
“at this moment, it is pushing down thousands of tons of air, and i am being held steady by the air at 10,000 metres.”
Isn't it romantic
If you feel that there is something, welcome, forward, follow-up. I'll tell you about one every dayScientific principlesI'll see you next time
