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B1 中级 英语 5:03 Educational

How do airplanes actually fly? - Raymond Adkins

TED-Ed · 2,277,315 次观看 · 添加于 3 周前

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B1

CEFR 等级

5/10

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字幕 (82 片段)

00:07

By 1917, Albert Einstein had explained the relationship between space and time.

00:13

But, that year, he designed a flawed airplane wing.

00:17

His attempt was based on an incomplete theory of flight.

00:20

Indeed, insufficient and inaccurate explanations still circulate today.

00:26

So, where did Einstein go wrong?

00:29

And how do planes fly?

00:32

Though we don’t always think of it this way, air is a fluid medium—

00:36

it’s just less dense than liquids like water.

00:39

Things that are lighter than air are buoyant within it,

00:42

while heavier objects require an upward force, called lift, to stay aloft.

00:48

For planes, this force is mostly generated by the wings.

00:52

One especially pervasive false description of lift

00:55

is the “Longer Path” or “Equal Transit Time” explanation.

00:59

It states that air molecules traveling over the top of a curved wing

01:03

cover a longer distance than those traveling underneath.

01:07

For the air molecules above to reach the wing’s trailing edge

01:11

in the same instance as those that split off and went below,

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