【新知讲解】流体压强

Q1. 飞机是如何获得向上的升力飞起来的？

Image showing the wing of an airplane flying above clouds.

Diagram illustrating the cross-section of an airplane wing (airfoil) and the flow of air around it. Streamlines show air flowing faster over the curved top surface and slower under the bottom surface, resulting in an upward lift force (indicated by a large upward arrow).

Q2. 下雨天雨伞为什么容易向上翻？

Image of a person holding a red umbrella in the rain.

Diagram illustrating the flow of air (wind) around an inverted umbrella. The wind flows faster over the curved top surface of the umbrella (which is now facing downwards), creating lower pressure above and higher pressure below, causing the umbrella to flip upwards.

1、流体：具有流动性的液体和气体统称为流体；

2、流体压强与流速的关系：

流体流速越大的位置压强越小，流速越小的位置压强越大；

3、流体压强的应用：

Diagram illustrating the cross-section of an airplane wing (airfoil) and the flow of air around it.
F1 represents the downward pressure force on the upper surface (low pressure due to high speed).
F2 represents the upward pressure force on the lower surface (high pressure due to low speed).
The net upward lift force is $F_2 - F_1$ .

飞机升力

Cartoon illustration of a high-speed train ("Fuxing Hao") arriving at a station. Several cartoon characters (Peppa Pig and friends) are waiting on the platform. A caption near the characters reads: "站台上不要逾越安全白线" (Do not cross the safety white line on the platform). This illustrates the danger of low pressure created by fast-moving trains (Bernoulli effect).

火车安全线

【剑指中考】

例题1: 飞机前进时, 机翼与周围的空气发生相对运动, 当气流迎面流过机翼时, 气流对机翼上下表面产生向上的压力差, 从而产生升力。能使图中的飞机前进时产生升力的秘密在于机翼, 则机翼的横截剖面图应该是 ( )

A. Image showing a thin, symmetrical, streamlined cross-section.

B. Image showing a typical airfoil cross-section, highly curved on the top surface and relatively flat on the bottom surface (designed for lift).

C. Image showing a thick, symmetrical, streamlined cross-section.

D. Image showing a rectangular cross-section.

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