The Forces on an Airplane: Aaron Johnson at K12Live! (MIT Museum Second Fridays, 1-10-14) - Free Educational videos for Students in K-12

The Forces on an Airplane: Aaron Johnson at K12Live! (MIT Museum Second Fridays, 1-10-14) - By MITK12Videos

Transcript


00:03	But so now we're actually gonna show you , we're
00:06	going to talk about some of the concepts that we
00:07	talked about in the video . We're not really gonna
00:10	be able to talk about weight . Everyone pretty much
00:12	knows what day it is . Perhaps especially after the
00:14	holidays were especially conscious of it . Uh , we're
00:18	not really going to talk about trust , we didn't
00:19	really bring an engine with us . We are going
00:22	to talk able to talk about the other two forces
00:24	lift and drag . So we need to get our
00:27	Minister wind tunnel set up . Oh , so why
00:31	we're doing this is probably a good idea if you
00:34	want a really good view to come up front .
00:37	So maybe you can sit in some of these seats
00:39	up front or just sit on the floor up here
00:43	because you really need to be closer to see what's
00:45	going on . Yeah , I don't know what this
00:56	is . Yeah , It was always going to bring
01:01	an extension cord . Alright , so essentially what this
01:06	is . This is a miniature wind tunnel . So
01:09	in aerospace engineering were both aerospace engineers . Uh We
01:12	use wind tunnels a lot to test airplanes . It
01:15	would be really cost inefficient if you built a giant
01:18	airplane and then fluid in a crash . And we're
01:20	like , oh , the design was really bad ,
01:21	we should change things . Uh So instead we test
01:24	models in wind tunnels . Uh We don't do it
01:26	so much anymore because we have computer programs which will
01:29	actually test out the aerodynamics . This is sort of
01:31	the field of research . Uh They'll test out the
01:33	aerodynamics oh and everything on a computer . So we
01:36	don't have to do a lot of wind tunnel testing
01:38	. But there great for student projects and demonstrations like
01:41	this . So this is a mini version that our
01:43	friends made . So what we're gonna do is we're
01:46	gonna put a couple of different things uh in the
01:49	wind tunnel , we're gonna turn on this fan here
01:52	, at the right side , it's gonna suck the
01:55	air through . These straws are just to straighten the
01:58	flow . So it's not all we call turbulent ,
02:01	which is when it's swirling and everything actually have these
02:04	on real wind tunnels , there's just a lot bigger
02:06	than this . So , the flow is gonna come
02:08	in here , flow over our square or are doing
02:13	whatever we have in there and then go out the
02:14	back and we're gonna use this dry ice . Uh
02:17	we're just gonna put hot water on it and it's
02:20	going to start to evaporate and create a lot of
02:22	smoke . And so we're gonna put this in here
02:25	, which will allow us to see the flow over
02:27	the square or the wing really help us to see
02:30	what's going on . So we're gonna turn this on
02:35	and so you can hear it start to go .
02:36	So I will turn the object and sort of talk
02:41	about it just that you want to do the ,
02:48	so as you can see , it's gonna start to
02:51	smoke a lot . So the first thing we're gonna
02:54	talk about is drag and so you can see ,
02:57	so the air is flowing through this way and if
02:59	I have to square like this , you can see
03:01	there's a big area that's perpendicular to the flow ,
03:05	so the air is going to come in and it's
03:06	gonna smack on the side of this square and it's
03:10	not really going to have anything anywhere to go .
03:12	You just put it out so there you can see
03:15	the flow coming in and it's coming in and smacking
03:18	into the side of the swear it has to go
03:20	all the way around the corner . So this has
03:23	a really high drag . It's kind of like when
03:26	you put your hand out the window straight up because
03:28	there's a really big area that the wind is smacking
03:31	too if we turn it sideways so that the air
03:36	at this point and it goes over to one of
03:38	the two sides , so that's a lot smoother flow
03:42	over the square . So this has a little bit
03:45	less strength , still a lot of drag because it's
03:47	a really big blocky object . This is why you
03:49	never really , you know , put some more water
03:53	in there , you really never have wings that look
03:56	like squares because they don't help your airplane fly very
03:59	well , They're pretty bad . So square is not
04:02	a shape that we see in aircraft wings . So
04:04	I'm gonna put in a different shape really quickly and
04:07	we're gonna put in a circle , which is another
04:11	shape that airplane wings don't have , but it's a
04:13	lot less drag . It's just been so it's sort
04:24	of spinning out chunks , surprise , You can see
04:27	the you can see that it's coming over and it's
04:33	going around the side , you can move it up
04:35	and down . I want to do that , just
04:36	move it until it goes over the top . I
04:42	don't know , more dries . Well let's try that
04:49	again because this is the coolest where we obviously don't
04:52	have airplane wings that are squares or circles because they
04:55	don't fly very well , they don't lose any of
04:58	that lift force that we talked about . So we're
05:02	gonna put in this airfoil and this airfoil comes in
05:04	its own special box . It's a very nice airfoil
05:07	. I was told not to mess this one up
05:08	, so that's cold . So this airfoil , so
05:20	we're gonna talk about how airfoils produce lift . So
05:24	you can see this is an airfoil . An airfoil
05:26	is essentially just a cross section of wing . If
05:28	you went out to an airplane and chopped part of
05:30	the wing off , they would chase you out of
05:32	the airport and probably be really mad . But if
05:35	you hear anything to that , I think about that
05:37	, what you have is this section here , which
05:39	is an airfoil . So we have a really ,
05:41	this is sort of a really exaggerated airfoil and you
05:44	can see how it's really curved on top and really
05:48	flat on bottom . Real airplanes don't look like this
05:51	. This doesn't fly very well either . This is
05:53	sort of the shape that you see . This is
05:55	like the exaggerated version . So one of the things
05:57	that happened that creates lift is the air flows faster
06:01	on top than the bottom . So you have the
06:04	air going over the top and it accelerates and it
06:07	goes slower on bottom . So that causes a lower
06:11	pressure on top . So there's high pressure on the
06:13	bottom of the weight and low pressure on top and
06:16	pressure wants to go from high to low . So
06:18	there's sort of a net pressure difference and it pushes
06:21	the airplane up . Um That's sort of one of
06:25	the mecca . It's not the only mechanism and that's
06:26	one of the ways that lift works . So we're
06:29	gonna put um actually , let's start with this big
06:32	airfoil . So we're gonna put this big airfoil and
06:36	what you should be able to see is , you'll
06:38	see , you know , we'll just turn it like
06:39	this sort of straight into the flow and this is
06:42	zero angle of attack . As we said in the
06:44	video , and you'll see the air going faster over
06:47	the top than the bottom . I should say .
06:49	You should see it just because of the curve design
07:00	just makes the air accelerates . It has a longer
07:02	distance to travel . The air is coming in at
07:06	the same speed . It has a longer distance to
07:09	travel over the top . So Well . All right
07:17	, well , that used to be working all right
07:22	, so you can sort of pull it up so
07:26	you can see you going over the top so you
07:27	can see it going over the top . It's going
07:30	faster than we move into the bottom . It's really
07:35	it's really teetering out there . We're not sure of
07:44	the correct . Yeah , Well that's way way ,
08:14	yeah , this is what science is . You can
08:16	just waiting to be like , oh well it's just
08:18	science . We're just trying things until until it works
08:22	, which is sort of doing a PhD is also
08:28	there were there were better ways . I think our
08:33	water wasn't hot enough I think yeah , you can
08:36	see the flow is really coming here and it's really
08:38	accelerating over the top and if you can't see ,
08:40	you're welcome to come off a little bit . Our
08:44	smoke screen isn't terribly fast , you're moving up and
08:48	down . You can sort of see the difference between
08:51	the bottom water . Wait , wait , this is
09:05	why we use real wind tunnels and not . Do
09:16	you want to get a little ? So does anyone
09:24	have any questions while we're true ? Alright , this
09:28	work . Any questions about airplanes or anything ? Yeah
09:32	, I always does this usually happen with dry eyes
09:40	for a second time using this one . So I'm
09:44	gonna say yes . So I don't feel that it
09:47	usually happens . It's not just that we're sure .
10:04	Let's just try a little bit . There's more mother
10:11	there . Well this video is funny , right ?
10:14	So yeah , it wasn't going to be lost .
10:28	Okay , so what we're gonna do is we're gonna
10:35	we're gonna start to turn it up and this is
10:37	increasing the angle of the attack . Like we said
10:40	in the video and it's increasing the drag because ,
10:44	you know , there's a larger area that's in the
10:46	flow . Does anyone remember what we called it ?
10:48	The video when you get too high of an angle
10:50	of attack and you start to use lift stall .
10:53	Yeah . So what you can see is here ,
10:57	we have to turn it up really high . You
10:59	would never if your airplane is ever like this ,
11:01	that's bad . Well , you can sort of see
11:04	the flow here is really swirling around and this is
11:07	what we call turbulent flow . This is bad .
11:10	You really want like this here , the flow is
11:13	really , it's attached to the wing is what we
11:15	call glam Inner uh , it's really attached to the
11:19	wing and there's a little turbulence and this is really
11:21	good because it gives us , but when we turn
11:23	it up really high and we get a lot of
11:26	turbulence , we lose lift and we also create more
11:29	drag . So this is bad . So you can
11:33	actually , like if you're flying in a really spicy
11:36	ever been in like a small like 2 to 4
11:38	person airplane , like a really small Cessna or something
11:41	. Ok . Yeah , a few people . So
11:43	my friend has when he took me out and he
11:44	was like , do you want to see what stall
11:46	feels like ? He's like no , I don't really
11:48	feel like dying . It's just like , you know
11:50	, land uh because if he did this and so
11:54	you sort of pitch up and up and up and
11:56	then eventually the aircraft obviously we're fine . I'm not
12:00	a ghost for anything , but the aircraft just sort
12:02	of starts to go down a little bit , you
12:04	can actually feel that stall and that loss of lift
12:07	. So it's pretty cool when you realize that airplane
12:10	is not going to fall into the sky . So
12:13	we're gonna try this little wing , which is also
12:16	a good song by Jimi Hendrix . What ? That's
12:18	unrelated . Um , I should say so , another
12:22	nice thing about airplanes . So people are always worried
12:24	like you're in an airplane up above , you know
12:28	, and like if the engines quit , everybody's always
12:30	worried like the airplane just gonna fall out of the
12:32	sky . Like Iraq , which actually isn't true .
12:34	Airlines can glide a lot . They can glide pretty
12:38	far because they , the thrust members said when he
12:41	comes from the engine and going fast helps to produce
12:44	lift , but you're still going fast even if the
12:47	engines go out , you still have a little bit
12:48	of lift and you can actually glide to the airport
12:51	. And there happened a couple airplanes that just ran
12:53	out of fuel . There's one in Canada , they
12:55	thought it was gallons and it was leaders and they
12:57	ran out of fuel but they are not blaming .
13:00	Today's . So here it is really an airport back
13:05	a little bit . Yeah , you can really see
13:07	the float . If we turn , see if you
13:11	come up really close , you can see , yeah
13:13	. So if you want to take a look ,
13:14	you can see there's really some gorgeous is happening here
13:17	at the back of the wing and that's turbulence and
13:19	that's bad because that's going to cause us to lose
13:21	lift . And also it's going to create more drag
13:24	and that's sort of an airplane starts falling out of
13:28	the sky . So that's not really good . Uh
13:32	Yeah , so commercial airlines are really cool because they
13:35	have these things on the back called flaps , which
13:39	are these like if you're ever landing and you hear
13:40	this mechanical noise , it's not the airplane coming apart
13:43	. Is these things at the back of the wind
13:45	extending , they sort of come off the back of
13:47	the wing like this . And they actually make the
13:49	wings longer and more curve , which lets you have
13:52	more lifted slower speed . So that's what we use
13:55	for takeoff and landing . Uh because when we fly
13:58	and cruise were flying it like what , 455 100
14:02	miles an hour , but you obviously can't take off
14:04	that fast , You can't drive that fast on the
14:06	ground . Uh Take out speed is about 120 miles
14:09	an hour . So we have these flaps , we
14:11	extend the airport , we get more lifted slower speed
14:14	. So that's how we take off straight once more
14:18	. Let's just put a little more water dry .
14:21	I supposed to do the , if anyone wants to
14:23	come up closer and sort of seeing the laminar flow
14:27	in the turbulent flow . Now be your chance .
14:30	We'll do it once more . I think we need
14:33	some more . Don't the water out in that bucket
14:35	, in this ball in the water . We still
14:42	got a lot of things that didn't work too .
14:46	But I think I just , okay , science ,
14:52	everybody just try it and eventually they give you a
14:56	PhD a story of the last four years . It's
15:05	right . So then any more questions about airplanes or
15:10	anything in general , you know , everybody wants to
15:13	go have dinner or are we just answered all your
15:16	questions . That's what I learned so much . No
15:19	further questions . What's happening , the first set of
15:25	airlines from today ? What are the innovations to help
15:31	them make them live ? Yeah , that's essentially it
15:37	. You know , aviation has been uh , here
15:40	. I'll do this demo . We have dry eyes
15:43	question . So as you can see , you know
15:44	, we have the laminar flow and turn it up
15:47	and there'll be a point there were getting it .
15:50	This is a pretty high angle with that . So
15:52	there you can really see , really see the border
15:56	season . It's also hitting the wing here , deflecting
15:59	. So this is , this is not good .
16:01	You're welcome to come up and take a closer look
16:05	. Uh , yes . So what's happened in aviation
16:07	in the past , you know , since the Wright
16:09	Brothers flew about 100 years ago , It's really about
16:12	efficiency . That's the main thing . So do we
16:14	know how to fly airplanes don't fly differently today than
16:18	they didn't like the thirties . Really . The differences
16:21	in efficiency , so working and making engines more efficient
16:24	. Boys , new airplane , the Dreamliner . It's
16:27	made out of all composite material . So it's very
16:30	little metal , so that's lighter and so you can
16:32	carry more passengers of less fuel and make the airlines
16:36	more , but they make the airlines more money ,
16:38	um , which I thought the $25 bag fees than
16:41	that . But apparently that's not enough . Uh ,
16:44	we have really efficiencies in the wings , efficiencies in
16:47	the engines . Like if you can get a 1%
16:49	increase in efficiency in your engine , you yeah ,
16:54	that's incredible . So it's just really minor increments ,
16:58	just sort of making bigger airplanes that fly with less
17:02	fuel . Another big increases , sort of the area
17:04	that we study is in the automation . That's ,
17:07	you know , back when , you know , you
17:08	had World War Two and those types of airplanes ,
17:10	the pilot was doing everything . They used to have
17:12	four people in the cockpit of like a Boeing 7
17:16	47 or something that would fly you from here to
17:19	maybe europe or Asia . There was a guy called
17:21	the navigator who would like half a map and would
17:24	say , you know , go straight until you hit
17:27	Portugal and then turn left . Uh , or you
17:31	could have someone called the engineer who would actually look
17:33	at these gauges that says , oh your engine is
17:35	functioning properly or your engine is broken . You should
17:37	probably land . That's generally a bad thing , especially
17:41	when you're on the ocean . But now they have
17:43	automation . Now the computers can take a look at
17:46	that . Uh , so on these long , well
17:48	on domestic flights , we only have two people in
17:50	the cockpit . And for these long oceanic flights we
17:53	generally have three people still just so someone can take
17:56	over . Uh yeah , actually airplanes can pretty much
18:00	take off , take off . The pilot goes down
18:02	the road , but it pulls the yoke back airplane
18:04	goes up into the sky . They can push a
18:06	button that says autopilot on and their blanket land without
18:11	the pilot really doing anything . Uh I was flying
18:14	back , I was flying from Austin to charlotte and
18:16	we landed and we went into these clouds and I
18:19	was like , oh we're in class , break out
18:21	of the bottom and I'll see charlotte below . And
18:23	the land was looking out the window and I saw
18:25	this light that was literally horizontal with the window and
18:29	that was all I saw was off log and there's
18:31	a light . I was like , I really hope
18:32	it's not like a building or something . Uh and
18:35	then I saw some more lights and we were on
18:37	the runway , there was very little visibility . We
18:39	really couldn't see anything . I don't know if it
18:42	was a legal landing was like at the bare minimum
18:44	but that was , you know , when you're trying
18:46	to land in fog or things like that . That's
18:48	when you're really desisted by the autopilot . You know
18:51	, in the early days pilots could really only fly
18:53	when they could see unless they were incredibly gutsy .
18:56	But now we can fly in all sorts of weather
18:58	conditions thanks to the automation . So that's been a
19:01	big sort of advance . Uh not with the aerodynamics
19:05	but more with sort of aviation as a whole .
19:07	And that's sort of the research that we work on
19:09	on human automation interaction . What should the human doing
19:13	? What should the autopilot yourself ? Yeah , that's
19:16	a great question . Uh any other questions uh what
19:21	I travel from Korea here or here in Korea ,
19:25	there is like a quite different and so much better
19:30	. Yeah , thanks to Yeah , I'm not sure
19:35	the specifics but I'm pretty sure it's yeah thanks to
19:37	the win because they're they're like the jet stream is
19:40	over the atlantic and you know just whether you have
19:43	a tailwind or or headwind it helps you to fly
19:46	because if you're flying with the wind it's just give
19:48	you an extra velocity boost . So yeah exactly .
19:52	Even going to the west coast , you'll get about
19:55	our difference in the travel between going west coming .
20:00	It also matters for how much fuel the airlines have
20:02	to burn going into when you can go as fast
20:05	. You can spend a lot more battery with battery
20:13	. Yeah so sometimes the plane , the Boeing 787
20:16	Dreamliner um they had lithium ion batteries and they caught
20:20	fire . I'm not sure the specifics it was I
20:23	think the contractor's fault . But yeah , I think
20:26	it was a new type of battery , right ,
20:28	wasn't it ? They were using the Dreamliner . It
20:32	was newly designed specifically for the type of battery was
20:37	common . I think it wasn't the battery goes like
20:41	this circuitry associated with . Yeah , I'm not sure
20:46	they fixed that . We were supposed to fly on
20:48	the Dreamliner and then they started catching on fire .
20:51	So yeah . Yeah , I think we probably don't
20:55	have at least one more question . How do planes
20:58	return ? Yeah . So how did things turn ?
21:00	So that's really that's actually a question . I like
21:03	a lot . Uh , it's not like evening .
21:04	So like if you're in a boat , like if
21:06	you've been in a boat , boats have runners and
21:08	essentially if you're going in a boat , you just
21:10	sort of turn the runner and the boat goes ,
21:12	you know , this one , you turn the other
21:14	the other way as the boat goes . The other
21:15	way planes actually they have runners , but they don't
21:19	really use them to turn like those two . They
21:21	essentially just banks . If you've ever been on a
21:24	plane , you probably experienced this Rihanna plane and it's
21:26	going along the banks and what this does is you're
21:30	just flying straight and level here . Why don't you
21:32	be the airplane to explain ? So Justin is an
21:34	airplane , you could be a you could be a
21:36	787 that hasn't caught on fire . So Justin's flying
21:41	straight and level the lift for this is sort of
21:44	like you're looking like head on their plane . We
21:46	should hold it horizontally , but we won't do that
21:49	, we're going to do that . So you can
21:51	imagine that here's the nose of the plane that goes
21:53	back like this . So he's flying horizontally . what
21:56	we call steady level flight . The lift vector just
21:59	go straight up , but he banks to the right
22:02	, a little bit of that lift vector is going
22:05	towards the center of the circle . There's still a
22:07	lot going up , but there's a little bit going
22:10	towards the center . And so that's gonna pull him
22:12	if you guys back up a little , that's essentially
22:15	gonna pull him in a circle like this . And
22:17	if he bangs , this is fun , if he
22:20	begs this way he turns like this in a circle
22:24	. So planes have a runner , but that essentially
22:26	just sort of keeps um then flying efficiently , the
22:29	real way they fly is they just bank and then
22:32	they automatically start to turn . So the next time
22:34	you're on an airplane , you'll notice that the airplane
22:37	doesn't start turning and then bag bags and then it
22:40	starts to turn , it naturally follows . Uhh ,
22:43	just following a question , how does it bank ?
22:46	Then there are these little things on the outside of
22:49	the wings called ailerons and they sort of , they
22:51	put one up and they put one now and that
22:53	changes the flow over the wing and then that you
22:56	get less with like if you get less lift on
22:59	this swing and more lift on this swing , it
23:01	will naturally bank like that . Or if you switch
23:03	, you get less lift here and more left here
23:06	. It's gonna impart a torque on there . Thank
23:09	you . I think we have to officially end ,
23:12	but we can stick around if you have any more
23:14	questions about airplanes . I think I know who they're
23:24	closing .

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