时间不够，要做作业，先翻到这里
Lift is created by forcing air downward. The pushing (accelerating) of the air downward creates an equal and opposing force upward on a wing (see Newton's third law.) The displacement of air downward during the creation of lift is known as downwash. The diversion of the airflow downwards can be seen to create a higher pressure below the wing and a lower one above it. An airfoil is so shaped to accomplish this as efficiently as possible. One puzzle is why the airflow "sticks" to the wing as it changes direction - this is known as the Coanda Effect, and the reason for it is not yet fully understood
升力是由向下气流的力造成的。推动（加速）向下的气流在机翼上造成一个大小相等方向向上的力（牛顿第三定律）。在产生气流的过程中向下流动的空气称为downwash(因机翼产生的下降气流)。向下气流的转移（？原文是diversion）可以被看成是增加了机翼上方（较低压强）和机翼下方（更高压强）压强差。机翼就是在尽可能有效提高这种现象的前提下制造的。有一个难题是：为什么气流改变方向时总是粘在机翼上——柯恩达效应，其原因至今不明。
Any shape will produce lift if tilted to the air flow direction (inclined) or cambered (curved). However, most shapes will be very inefficient and waste a great deal of energy in the creation of drag. Lift itself creates drag - this is called lift-induced drag, or just induced drag.
只要与气流方向成一定倾斜角，任何外形都可以产生升力。然而，大部分外形都是非常缺乏效率的，而且会在阻力增加的过程中损失大量能量——这被称为诱导阻力。
The force on the wing can also be found using the pressure differences above and below the wing. This method of explanation is mathematically equivalent to the Newton's 3rd law explanation as developed above. The relationship between the velocities and pressures above and below the wing are nearly predicted by Bernoulli's equation. The differences between the Bernoulli-predicted values and the true values are small and related to viscosity, which is neglected in the Bernoulli equation. However, one common misconception is that the pressure differences result from the velocity changes needed for the air that separates at the front of the airfoil to meet at the trailing edge. This does not happen, in fact, if it were to happen, no lift would be generated, as explained in the circulation section below.
在机翼上作用的力同样可以从机翼上下的压力差找到根据。这种解释方法与上面述的牛顿第三定律的解释在数学上是等价的。伯努利方程对机翼上下面速度和压力的关系作了相当接近的预言。伯努利预言的值与真实值之间有微小的差别，这是由于在伯努利方程中忽略了粘滞性。然而有一种误解是，压力差的成因是机翼前沿分开的并在机翼后沿汇聚的气流的速度的改变。这种情况并不会发生，实际上，如果它发生了，就不会有升力产生，下面解释环流时将会解释
不知道这段话和发动机有什么关系，第一段我的理解是抽象的把气流和机翼看成两个相互作用的质点系，然后用牛顿第三定律解释，不清楚是怎么扯到发动机喷流上的
至于那个球，我觉得应该是反过来理解——必须是能和空气成一定倾斜角的外形。我不认为球能够做到。
像“Any shape will produce ...那么怎么解释这个shape? 对于一个球而言无所谓迎角呀，只要air flow direction 和球的垂直轴线方向重合就行了 ”这种理解我不知道意义何在
ps:靠，早上起来发现第一段有致命错误，改之。本人英语不好，而且只是随便写一下中文意思，将就着看吧，有刺请尽情地挑
