s**x
发帖数: 7506 | 1 How do airplanes stay up?
To overcome the forces of drag and gravity, an airplane must generate two
forces of its own: thrust and lift.
Thrust is the force that propels an airplane forward on the runway. By
Newton's third law — every action has an equal and opposite reaction — the
plane's engine generates forward thrust by spewing fuel backwards. Next, as
the plane hurtles down the runway, each of its wings slices the air into
two streams, one that flows above it and the other, below. The wings are
shaped in such a way that the air flowing over them is ultimately deflected
downward, and, again because of Newton's third law, the downward motion of
the air causes an equal and opposite upward motion of the plane. This is
lift. [Do Planes Get Struck by Lightning?]
Every airplane has a specific takeoff speed — the point at which lift
overcomes gravity. That critical speed changes based on how much a
particular plane weighs. The plane's engine, meanwhile, has to work to
provide enough thrust to overcome drag — friction with the air. |
s**x
发帖数: 7506 | |
m****r
发帖数: 6639 | 3 this is mostly inline with my understanding. but then, i am not an engineer.
the part that i am not sure is how the wing generates lift. I had thought,
it works by passing more air below the wing, and less air above the wing,
and as a result, generates a vacuum above the wing, which turns into lift.
【在 s**x 的大作中提到】
: is this right?
|
d**n
发帖数: 3172 | 4 这段有点问题
The wings are
shaped in such a way that the air flowing over them is ultimately deflected
downward, and, again because of Newton's third law, the downward motion of
the air causes an equal and opposite upward motion of the plane |
b*******r
发帖数: 6655 | 5 这世界上还有人知道牛顿？他算什么东西，没有苹果他发现得了什么？没有苹果亚当夏
娃还在两小无猜呢，还不过来拜谢乔老爷创造了人类！ |
c**d
发帖数: 3888 | 6 No problem with this. Part of the lift is generated by Bernoulli, part by
the downward defelction. It's why an inverted airplane can still maintain
lift
deflected
【在 d**n 的大作中提到】
: 这段有点问题
: The wings are
: shaped in such a way that the air flowing over them is ultimately deflected
: downward, and, again because of Newton's third law, the downward motion of
: the air causes an equal and opposite upward motion of the plane
|
c**d
发帖数: 3888 | 7 Planes do get struck by lightning. Very loud but usually very little real
damage
the
as
deflected
【在 s**x 的大作中提到】
: How do airplanes stay up?
: To overcome the forces of drag and gravity, an airplane must generate two
: forces of its own: thrust and lift.
: Thrust is the force that propels an airplane forward on the runway. By
: Newton's third law — every action has an equal and opposite reaction — the
: plane's engine generates forward thrust by spewing fuel backwards. Next, as
: the plane hurtles down the runway, each of its wings slices the air into
: two streams, one that flows above it and the other, below. The wings are
: shaped in such a way that the air flowing over them is ultimately deflected
: downward, and, again because of Newton's third law, the downward motion of
|
s**x
发帖数: 7506 | 8 我记得以前读过说是因为飞机上面的空气流动的快（上面曲度大）， 下面的流动的慢
而产生的压力差。
engineer.
,
【在 m****r 的大作中提到】
: this is mostly inline with my understanding. but then, i am not an engineer.
: the part that i am not sure is how the wing generates lift. I had thought,
: it works by passing more air below the wing, and less air above the wing,
: and as a result, generates a vacuum above the wing, which turns into lift.
|
c**d
发帖数: 3888 | 9 it's called Bernoulli and is only part of the equation. In fact it's no
factor in supersonic and inverted flight. Think about it
【在 s**x 的大作中提到】
: 我记得以前读过说是因为飞机上面的空气流动的快（上面曲度大）， 下面的流动的慢
: 而产生的压力差。
:
: engineer.
: ,
|
d***e
发帖数: 13568 | 10 就好比飞机竖起来？？
【在 c**d 的大作中提到】
: it's called Bernoulli and is only part of the equation. In fact it's no
: factor in supersonic and inverted flight. Think about it
|
|
|
c**d
发帖数: 3888 | 11 Thrust = lift in vertical flight
Inverted means the aircraft is flying upside down
【在 d***e 的大作中提到】
: 就好比飞机竖起来？？
|
m****r
发帖数: 6639 | 12 right. same thing.
【在 s**x 的大作中提到】
: 我记得以前读过说是因为飞机上面的空气流动的快（上面曲度大）， 下面的流动的慢
: 而产生的压力差。
:
: engineer.
: ,
|
d**n
发帖数: 3172 | 13 那段的说法是有问题的。shape是提供气压差。攻角才是他想说的deflection |
s**x
发帖数: 7506 | 14 你说的对。
下面的解释好像不错, 按照上面的解释我还以为机翼上面有缝隙把空气导入下面呢。 应该就是这个攻角
了。
我们在水面上扔石头片使石头片飞起来应该是同样的道理。
http://wings.avkids.com/Book/Flight/instructor/forces-01.html
【在 d**n 的大作中提到】
: 那段的说法是有问题的。shape是提供气压差。攻角才是他想说的deflection
|
F*********e
发帖数: 1765 | |
