- Have you seen this man?
- Not so fast.
- Hi, my name is Rhett Allain.
- [Announcer] Rhett is a physics professor
at Southeastern Louisiana University.
- Today I'll be breaking
down amazing feats of physics
from superheroes in movies and television.
Superhero landing, Deadpool.
- Go get some.
- Superhero landing.
She's gonna do a superhero landing.
Wait for it.
Whoa, superhero landing.
You know, that's really
hard on your knees.
- You know, one of the
great things about Deadpool
both in the comics and in the movies
is that he breaks the fourth wall
and interacts with the audience.
- I know, right?
- In this case, he talks
about the superhero landing.
- Superhero landing.
She's gonna do a superhero landing.
Wait for it.
- The idea is a superhero
lands with one knee,
one fist and a foot on the ground.
So three contact points,
but it's a very sudden move.
It's not like a normal landing,
it does look really cool
and it happens all the time.
And is that better than
the way a normal person
would hit the ground?
The answer is no.
- You know, that's really
hard on your knees.
Totally impractical, they all do it.
- So you gotta think about
the forces acting on a person
while they're landing from
falling from somewhere.
The key is to have the
force as small as possible.
One way to do that,
is to increase the distance
over which you stop.
So if I jump and land on the ground,
I let my knees bend,
and my center mass moves
down while my knees bend
increase the distance over which I stop
and decrease the force.
There's a thing called a
parachute landing fall,
and you don't even stand up.
You hit, you bend down, you
roll over on the ground,
and you increase the distance
over which you stop even more.
That's the best way to do it.
The superhero landing, it's
just gonna be a bad idea.
- And we all know how this turned out.
- Kinetic energy, Black Panther.
- Hey, look at your suit.
You've been taking bullets
charging it up with kinetic energy.
[engine roaring]
- Kinetic energy is a quantity you can use
to describe objects in motion.
We have momentum, which
is mass times velocity
and then there's kinetic energy,
which is one half mass velocity squared.
- Show off.
- You know, kinetic
energy isn't a real thing.
It's a way to view nature.
It's a way to view interactions.
So anything that's moving
would have kinetic energy.
If I take a baseball and I throw it,
it's moving, it has mass,
so it has kinetic energy.
Black Panther's suit somehow
has an interaction between
the bullet and the suit
to take the kinetic energy of the bullets
and store it in some
type of internal battery.
And then once he has
enough energy stored up,
he can release it in an
energy polt of some type
to do whatever he wants.
I'm not sure exactly how it works.
That's what makes him Black Panther
and the technology of Wakanda is beyond me
to fully understand.
Recoil, Wonder Woman.
[gun fires]
So what is recoil?
Suppose I am standing on a frozen lake
and I have a basketball or
some heavy weighted ball
and I throw the ball.
Well, the balls momentum is gonna change
because I exert a force on it.
But the ball pushes back
on me with the same force.
So I'm gonna have the
exact same change momentum
that's gonna make me move back.
- Of course, it makes complete sense.
- This is the idea of recoil.
When you throw something one way
you go back the other way.
So a bullet has momentum.
It's moving, it has mass has velocity,
but it turns out that
it's moving really fast
but it has pretty low mass
and it doesn't have that much momentum.
If you collide a bullet with a bracelet
or a person in some way,
then that person would have to recoil
with the same momentum.
But the person has such a large mass,
the recoil velocity would be super tiny.
And so you don't really get
recoil from normal bullets
when they hit people.
So in this case, Wonder
Woman deflecting a bullet
it should be fine.
- Is there anything else
you wanna to show me?
- Contact area, Justice League.
- I'll take the ones on the right.
- The Superman building
thing is impossible.
Forget about the flying, forget
about the super strength.
Even with that he couldn't do this.
So imagine you had a jello cake.
It's like a big blob of jello this big.
- Is this a bad time to
bring up my blood sugar?
- And you want to lift up
the jello with a toothpick
by pushing on the bottom,
the toothpick would just
go right through the jello.
On top of that, the jello would
probably break in half too.
So both of those things are a problem.
Superman's pushing in the
middle of the building,
trying to support the whole thing,
he would just poke right
through the whole thing
and the building would fall.
If he wants to actually lift the building,
he needs to increase the contact area,
either get bigger hands,
which that's probably not gonna happen.
Or he could possibly have some cables
that attach to multiple
locations on the building,
and then lift it from the top.
Maybe it doesn't look as cool,
but it'd be more plausible at least.
- Weird in so many ways.
- Strength, Spider-man Homecoming.
At the beginning, Spider-Man uses his webs
to connect one side of
the boat to the other
in an attempt to prevent
it from falling apart
and it doesn't work.
- Yeah, Spider-Man.
- It could be any number of reasons.
Particularly, he just
doesn't have enough webs
to actually exert enough
force between the two halves
to prevent them falling apart.
The ultimate tensile strength,
the point at which the tension breaks
where the string breaks
for Spider-Man's webs.
I mean, you first need
to know what it's made up
and then you need to
know the diameter of it.
It's really difficult to
estimate how much that could be.
A better way to approach this,
would be to calculate the tension
that he exerts on the boat when it breaks.
The more they lean,
the greater the gravitational
force is on that piece
to pull it apart and
you need a lot of force
to keep these two things together
and maybe his webs just aren't
strong enough to do that.
- [Karen] Great job, Peter.
You're 98% successful.
- 98?
- I suspect the 98% means
that the total force needed to
keep one side of the boat up
is 98% of what you need to
prevent it from falling over.
If the force isn't great enough,
the boat tilts and it stretches that web
and eventually the web breaks
and then you have no force from the web
and that makes more webs break
and have a sort of cascading failure.
- Hi, Spider-Man.
Band practice through?
- The Iron Man suit may be more successful
at pushing the boat back
together for a couple of reasons.
Number one, it's possible
that his many micro thruster rockets
that attach to the side of the ship
are just stronger than Spider-Man's webs.
The second big thing
is that those forces can keep
moving as the boat moves,
whereas Spider-Man's
force is a static force.
Once you stretch past that, it
can't pull it back together,
it just prevents it from
falling apart further.
The ship floats
because it prevents
water from getting inside
and makes it overall effective
density less than water.
Once you violate the integrity
of the hole, game's over.
That thing is gonna sink really fast.
I don't think Spider-Man
is gonna have enough time
to push it back together,
I don't think Iron Man's
gonna have enough time
to push it back together.
Now, it's just a movie
so we're okay with that.
- What do you want me to do?
- I think you've done enough.
- Terminal velocity, Captain
America, The Winter Soldier.
- Was he wearing a parachute?
- No.
No, he wasn't.
[dramatic music]
- So when Captain America
jumps out of the plane,
there's really two forces
that come into play.
The first is the gravitational
force that pulls him down.
But there's another force
as he starts to fall
and increase in speed, there's
an air resistance force.
He's colliding with the air molecules
and those air molecules push back on him
in the opposite direction
that he's moving.
And in fact, it gets to the part
where it is the same as
the gravitational force.
Now he has an upward pushing force
and a downward pushing force
that are equal in magnitude.
With equal magnitude forces,
he moves at a constant speed.
We call this terminal velocity
because he doesn't get any faster.
When Captain America
first leaves the plane,
he starts off in a standard
skydiving position.
This position allows
the largest surface area
for the highest air resistance force
and therefore the lowest
terminal velocity.
It also allows you to
move your hands in a way
that you could actually
control your motion
by pushing the air in
different directions.
Towards the end of the jump,
he actually goes into a
more vertical position.
This decreases the surface
area that collides with the air
and makes him fall even faster.
- Dude, you're a lot
heavier than you look.
- I had a big breakfast.
- He wants to hit the water feet first.
So he flips over, hits
the water feet first
in like a pencil, dive or pencil jump
and the nice thing about the
feet first vertical position
when hitting the water,
is that it will make him penetrate
the deepest into the water
which increases the
distance over which he stops
and decreases the stopping force
and gives him a better
chance of surviving.
I mean, it's Captain America,
so he's probably gonna
survive no matter what.
Net force, Iron Man three.
- Listen to me, see that guy?
I'm gonna swing by, you're
just gonna grab him.
I'll electrify your arm,
you won't be able to open your hand.
We can do this Heather.
- Once you start having multiple people
in a chain hanging together,
the person on the bottom,
they're just hanging like a normal person.
The next person has to pull
with the force equal to their own weight
and the force of the person
pulling down below them,
which is their weight.
The third person has to pull
with the force of three people
and you can see,
it starts getting really
large and uncontrollable.
Iron Man wants to solve this problem
by essentially electrically
shocking their muscles
into contracting so they can't let go.
- I'll electrify your arm,
you won't be able to open your hand.
- I don't think that would work
for a number of reasons.
- I get a lot of this, it's okay.
- First if you get like
five people in a line,
it's probably not just about muscles,
things start to break in human
arms and it wouldn't work.
The second thing is that
you can have an electrical shock
make people's muscles contract
but the problem is that you
normally need a closed circuit
you need a path for
the current to go there
and all the way back
and he just has a chain.
There's no way for the current
to get back to Iron man
and use his power supply to
force this shock gripping.
- Nice guys work guys.
Excellent, good team
effort all around, go us.
- Disintegration, The Boys.
- Poster.
- Hey, don't you ever besmirch Billy,
- I can't stop, I can't stop.
I can't stop, I can't stop, I can't stop.
- So A-Train's running really quick
and he runs into a girl,
what would really happen?
I mean, it's such a hard question
because it really depends on A-Train.
Is he invincible
or is he like just a
really fast, normal human?
If he's a really fast, normal human,
colliding with a stationary human,
they would both have the
same amount of damage
because if he pushes on her with a force,
she pushes back with the same force.
So whatever happened to
her would happen to him.
In the clip, she just turns into goo.
So clearly, he has some other powers
other than just being super fast.
Would he just push right through her
or would which she recoil?
Well, it really depends on again,
how fast he's going and
how he actually hits her.
If one part of him hits her,
before the rest of him does,
he could essentially poke through her.
I know that's kind of gross
and once he's done that
he kind of disables the
integrity of her body,
such that it's possible
she could go splattered
all over the place.
Oh, watching that clip,
there is one issue that is weird.
If he's running this way and hits her,
why did some of the blood
go back on on her boyfriend?
It appears that he hitting her
would push all the blood
in the same direction
he was moving.
So, I mean, it's kind of a gross clip,
but it shows an important
point in the story
and that the superheroes
aren't always nice guys.
- Sorry about what happened
to your girlfriend, all right?
- Running on water, The Incredibles.
[laughs]
[dramatic music]
So let's say you wanna run on water,
you need an upward force
to counteract the gravitational
force that pushes down.
One way to do this would be
kind of like slapping the water.
If I hit the water with my hand or foot,
then the water pushes up on me,
but it's not a huge force and
it doesn't last for very long.
- I don't know, I don't
know how he does it.
- That means that you have
to hit the water really hard
and then hit it again really hard.
So you really got to move your feet
back and forth super quick
in order to get this whole thing to work.
- You must have been booking,
how fast do you think you were going?
- I mean, I don't think a
normal person can do it,
but clearly Dash can do it.
So when he stops and kind of hovers there
for a little bit on the water,
I think it's the Wile E. Coyote effect.
So if you remember,
Wile E. Coyote would
chase the Road Runner.
He'd go off a cliff, and then he'd say,
"Well, I just realized
I'm not on the ground."
And then he falls.
It's very dramatic and it's kind of funny,
and I think that's exactly
what happens with Dash.
Of course, as soon as he stops
he would start sinking into
the water and fall down.
But it's comedic effect.
- [Robert] Well, what are you waiting for?
- I don't know, something amazing I guess.
- Flying, Iron Man.
- Ready,
and three,
two,
one.
- In this scene,
Tony Stark is testing
out his Iron Man suit.
He had built one before,
but it wasn't as
sophisticated as this one.
- Not bad.
- So he needs to make sure
that thrusters are configured
properly to allow him to fly.
So imagine you had like a pencil
and you wanna hold it
on your hand right here,
and you're holding it from the bottom.
If you push up, it's very
easily just gonna tip over.
And so rockets from the bottom of a device
are a little problematic.
Real rockets do this by having
gimbals on the thrusters
that can change the direction very easily.
But there's another solution,
and that's to have a higher thruster
and that's what Iron
Man does with this hand.
When his hands are higher up,
then the thrust is above the center mass,
and it makes it much more stable.
And on top of that,
he has his hand further
apart from his body
and that further increases stability.
In fact, there's a guy that has
real life Iron Man suit type flying,
and he uses jets on his hands,
and it's much more stable than
putting them on your feet.
So this is exactly how I would do it
if I was gonna do it.
Impact force, Guardians of the Galaxy.
- No Groot, you can't.
You'll die.
- I'm not sure what exactly
Groot does in this case,
but if he stays completely
rigid as a rigid sphere,
then it's not really going
to help people inside.
Now, if he has some type of,
I don't know, in a car,
we call it a crumple zone
where the car actually changes dimensions
and crumples up during a collision.
This would increase the
distance over which it stops,
which would decrease acceleration
and it would make it more
survivable for the people inside.
Another aspect of this cage idea
could be one to protect
from things like debris
that gets thrown around during the crash.
That would definitely work.
I mean, if you have a shell around you
and something comes flying
in, that shell could block it.
It's not just that you
want wood to be strong,
you definitely want it be flexible group.
Groot maybe he's like, can pick,
maybe he can pick what
kind of wood he grows into
so he could make it both
flexible and strong,
depending on the situation.
- Thank you.
See, Groot's, the only
one of you who has a clue.
- If I was Groot, which
I'm clearly not Groot.
- I am Groot.
- I would have like things
go down below the sphere
that you couldn't see
and have those impact
with the ground first
and have them kind of be your crumple zone
and then keep the sphere
rigid to protect from debris.
And then you'd have a
rigid part as a sphere
and then a springy part below.
- Force pairs, The Defenders.
So in this scene from The Defenders,
we have Jessica Jones, super strong,
and Luke Cage, super strong.
And when they punch,
they really would have to
consider what angle they push at.
If I push with some super large force,
then that same force is
gonna be applied to me
because forces come in pairs.
Forces are always an
interaction between two objects.
So if I punch horizontally,
the person could go
flying across the room,
but I'd go flying back the other way
and that may be effective,
but it wouldn't look cool.
There's a better way to punch.
If I was a super powered
puncher and I punched up,
then that person would push down on me
and I would get pushed into the floor,
but I would not get pushed back.
So if you're a super powered person,
you can't just go around
punching like a normal person,
you have to think about the
consequences of your actions.
But we should probably all do that anyway.
- Jessica?
- Luke.
- [Luke] How you been?
- Long story.
- X-ray vision, Man of Steel.
- Are you alright Clark?
- So this is the part where Clark Kent
starts to realize that he has powers
and one of those powers is X-ray vision.
How does X-ray vision work?
I think the first question
is, how does vision work?
We see things because
light reflects off of them
and enters our eye.
Or maybe it's a light source itself,
but light has to enter your
eye in order to see things.
X-rays are just another type of light
with a smaller wavelength
than visible light.
But in this case, how does
Superman have X-ray vision?
Is stuff coming out of his eyes
or is stuff coming into his eyes?
If X-rays are coming out of his eyes,
he can't see them, it's just shooting out.
There are X-rays around,
background radiation.
It's not very much
and that could pass
through people's bodies
and he could see them.
But overall, it's definitely
a problematic thing
to be able to see through
people with just your eyes.
Windup, Avengers Endgame.
- I knew it.
- So Captain America has Thor's hammer,
and he's trying to hit Thanos,
he could just hold the hammer
and swing his whole arm and hit him
but by winding up the hammer first,
it's going in a circular motion,
the hammer is actually
going at a greater Speed.
If he times it just
right, his arms moving up
and the hammer is moving
up relative to the hand.
So that gives it a much greater speed
on impact with Thanos' head.
So greater impact speed would
mean a greater impact force
and hopefully knock him down in this case.
There's no real benefit to
spinning it multiple times,
except for the main
benefit that it looks cool.
And if you're a superhero, and you're in,
you know, a big battle number
one, you gotta look cool.
- Give me that.
You have the little one.
- [Announcer] Conclusion.
- I think these are just great examples
of even if they're not real physics,
physics is still all around us.
And we can find it in
the most trivial things,
even superhero movies.
So physics in movies, I'm all for it,
even if it's not 100% correct,
because what if you did have
completely realistic physics
in superhero movies?
Might not be that much fun.
We go to the movies, not
for the correct physics.
We go there because they don't
have correct physics really
and I'm fine with that.
