Kind: captions
Language: en
Shh. [sighs]
I've snuck into Minute Physics Studio to
explain how a wing actually works. Hang
on. Something doesn't feel right.
Ah, that's better. Now, everyone knows
that a wing generates lift due to its
characteristic shape. Since air travels
farther over the top of the wing, it
must go faster than the air underneath
so that both streams meet up
simultaneously at the trailing edge. And
according to Bernoli's principle, faster
flowing air exerts less pressure than
the slower air beneath the wing. This
pressure difference creates an upward
force, lift. Job done, right? Nope. This
simple explanation taught in many
textbooks and classrooms has obvious
problems like how could a plane fly
upside down? Some planes like the Wright
brothers had nearly flat wings, so
presumably air would travel the same
speed over both sides and there would be
no lift. Plus, experiments show that air
streams don't meet up at the back of the
wing. Air over the top goes
significantly faster, reaching the
trailing edge first. So, how does a wing
actually generate lift? Well, the key is
the wing must deflect air downwards.
This can be achieved using asymmetric or
cambered air foils or by increasing the
angle of attack. Air under the wing is
deflected down and by the effect, air
above the wing is guided along its
surface and down as well. [music] Since
the air is slowed and deflected down by
the wing, it pushes the wing up [music]
and back, lift and drag. This is in
accordance with Newton's third law of
motion. But hang on, if you can explain
lift only using the deflection of air
and Newton's laws, then the Bernoli
explanation must be completely wrong.
Well, no. Air over the top of the wing
does go faster than air beneath,
creating a pressure difference that
generates lift. Then [music] this
Newtonian explanation is unnecessary
rubbish. And the original explanation
was right. But that's not true either.
The original explanation incorrectly
assumed that air over and under the wing
must reconnect at the trailing edge. And
there was no mention of deflecting air
down. Each explanation done correctly
completely accounts for the lift
generated by a wing. [music] They're
just two different ways of looking at
the same thing. So next time someone
brings up the standard misconception,
you can tell them that explanation just
doesn't fly.
And if you like that, you've got to
check out Minute Physics. I have total
respect for a guy who does this every
week. Sincerely, a collection of
particles known as Derek.
[music]