Diandra Leslie-Pelecky: I thought that was really creative
and totally possible.
My name is Diandra Leslie-Pelecky.
I have a PhD in physics, and I started off my life
as a condensed-matter physicist working in nanomedicine.
Along the way, I ended up writing a book called
"The Physics of NASCAR."
So today I'm gonna use that knowledge
to talk to you about some clips
from "Fast and Furious."
This is one that is a little difficult to analyze,
because you're not quite sure how long they're falling.
It could be anywhere from 11 seconds to maybe 15 seconds.
That's a really long time to fall.
I calculated out
what Dom's terminal velocity would be,
and that's biggest velocity you can fall
given that drag gets bigger as the speed goes up.
And he almost approaches it.
After 11 seconds,
Dom would be going 124 miles per hour
when he hit the water.
He would have fallen about 1,775 feet
at that point.
Now, 124 miles per hour into water,
maybe that's survivable.
Laso Schaller holds the record for the highest jump.
That was from 193 feet.
He hit the water at 76 miles an hour.
He broke his right clavicle and dislocated his pelvis.
The Golden Gate Bridge is about 245 feet.
People hit the water at 86 miles an hour.
Only 5% of the people who jump survive.
So the probability of them surviving is pretty small.
They built a launcher and took this beautiful
1966 Corvette and actually launched it
off the side of the cliff,
and then they had stuntmen
who did it separately from the car
because being hit by a car midair
would be worse than actually hitting the water.
And so they had the stuntmen do it,
but the stuntmen were on cables.
Then they came back, did it on a green screen
with the actual actors, who were, you know,
maybe eight feet above the ground.
But this one I think I would have to give a score
of two, because there's absolutely no way
they could've survived a jump that long.
So, this a 1969 Camaro.
It's got a mass of about 3,500 pounds.
So, they're hitting 90, so you know
the boat's going at least 90 miles an hour.
One of the things that you notice is that
when the car and the boat are both speeding along,
they're parallel to each other.
Now, how they all of a sudden get behind the boat,
I'm not actually sure how that happens.
But let's assume they can do that.
When they take off, they're going at approximately
45-degree angle off this ramp,
and they're going 120 miles an hour.
So not all of the speed
is taking them in a horizontal direction.
So I've taken cosine of 45; they're only now going
about 78 miles per hour toward the boat.
Now, that's a problem,
because the boat and the car looked like
they were going the same speed.
And the problem is, if the boat's going 100 miles per hour,
it'll be 1,200 feet from the shore.
The problem is, the car can only go 945 feet
in the time it's in the air.
There's actually no way
that the car could make it onto the boat.
Let's pretend the boat is only going 78 miles an hour,
because if they are, it's totally possible.
It is going fast enough, and it makes up
all the distance between it and the boat.
So if you include drag,
they're gonna lose some of their speed
due to air resistance.
They're still gonna hit that boat
at around 105 miles per hour.
The kinetic energy of the car
and the guys in the car, at that point,
is equal to about a fifth of a pound of TNT.
Some of that goes into wrecking the boat
and wrecking the car, but not all of it.
Which means some of it is gonna go into the guys,
and they're gonna have a whole lot worse
than a broken arm.
I think I'd give it probably a seven out of 10,
because it's possible it could happen.
They had to modify this tank
so it could go 60 miles an hour,
'cause they normally only go 30 miles an hour.
Dom, we'll assume his car was going 60 miles an hour,
so when he left it, he was going 60 miles an hour.
So you can look at conservation of momentum
and figure out that by the time they hit and continued on,
they were probably going around 40 miles an hour.
So a little bit of change in speed,
but the problem is when he hit the car
going 40 miles an hour, and she is about 120 pounds,
he's about 225, so you're talking about 340 or so pounds.
You're gonna be hitting it with an acceleration
of almost 100 g.
They have no protective gear.
So, you know, race-car drivers
routinely survive hits of 100 g.
They've got a big car around them.
And maybe it's possible that Dom could launch himself
at just the right angle to intercept Letty.
And then maybe it's possible that
that path took you onto the second bridge
instead of over the first one,
and maybe it's possible that there happened to be a car
at the point where they were landing,
and maybe it's possible
they survived hitting the car together.
Each one of those things might have happened,
but all four of them together
is just too much of a coincidence.
Once you're in the air, you cannot steer.
So if you misjudge in any way,
you're gonna miss her.
Now, if you watch baseball players,
they develop this very intuitive ability
to know the arc of a ball.
And after all, it's just a parabolic motion.
Maybe just Dom understands physics so well
that he knew exactly where to launch himself.
And if you talk to a race-car driver,
they would be able to understand centripetal acceleration
and explain it to you. Again, no equations,
but they get this intuitive understanding for it.
So, it's just possible, maybe Dom has
rescued enough people who are flying through the air
that he understands how to do it.
Hollywood has its own physics.
One of the rules is they have time dilation,
which is that when something really exciting is happening,
it can take as long as you want it to take.
Slowing down, let's say 120 miles an hour,
and I pick that number only because
that'll tell you, at 120 miles an hour,
the car is going two miles every minute.
So for every minute of that clip,
you're traveling two miles.
The longest airport runway in the word is 3.4 miles,
which means if they were on that runway,
this still could take 1.7 minutes.
And it doesn't.
It takes a lot, it takes, like, 11 or 12 minutes,
which would result in just this unfathomably long runway.
OK, so Dom is driving a 2012 Dodge Charger,
and let's pretend this is a super-reinforced version
of a Dodge Charger.
He doesn't have a lot of time to get up speed.
Because he's only got the inside of a plane,
and as you saw from the fight that was going on,
there's not a lot of room.
I think I have to give a one.
Just because here,
they stretched my ability to ignore reality
just a little further than I'm capable of doing.
Try to figure out how much that vault weighs,
according to the storyline.
So, we're gonna assume it's a 5-ton vault.
That's about 10,000 pounds.
There's $100 million in $100 bills.
That's gonna give us another 2,200 pounds.
Dom is 225 pounds,
and the car is 4,180 pounds.
That gives us a total weight of 16,605 pounds
that his car has to accelerate.
If you ever tried to move something heavy,
like a refrigerator or a bookcase,
you push on it, and it doesn't move.
And you push harder, it doesn't move.
And you push harder, and finally it moves.
That moment when it moves,
you've just overcome the static frictional force.
The static frictional force is higher
than the kinetic frictional force.
And what that means in real-people talk
is that once you get something moving,
it's much easier to keep it moving.
So the question is,
is it possible for this 2010 Charger SRT
to overcome the friction needed to move?
So we're gonna calculate how long it would take him
to accelerate up to 50 miles an hour.
We've got the 425-horsepower car
accelerating 16,605 pounds.
And it turns out that would take about 5.86 seconds,
which is a little longer than it took him
to actually do it in the movie.
So the fact that he got the car accelerating that fast,
that definitely couldn't happen in real life.
But that's without friction.
So once you put friction in,
what you find if you calculate
is that the coefficient of friction between, like,
steel and asphalt is pretty high.
And you probably could not,
even with a nitrous oxide boost,
get the vault moving.
So, once you got it moving, you could keep it moving.
What the folks have said who did this stunt,
they found the same thing.
They learned a lot about static friction the hard way.
And they actually put a slippery material
on the bottom of the vault to get it moving.
But one of the problems with that
is when you make something easier to start moving,
you also make it easier to stop moving.
And my understanding is they were very surprised
when they thought it would come to a stop
and it took a lot longer to stop than they thought it would.
The other thing is the question of,
you have this fairly small mass of a car and Dom.
That's about 2,000 pounds.
And the mass of the vault,
which is about 15,000 pounds.
So you've got something that's seven times bigger
than something else.
Now, think about when they're coming down
and then Dom starts, stops, and he lets the vault
sort of swing around.
The vault is, you know, seven times heavier
than Dom and his car.
And I just don't buy that he has enough traction
to swing the vault without the vault pulling his car along.
Making these stunts work in real life,
with practical effects and not CGI,
so they built something like seven or eight different vaults
with different weights so that they could do
all the different parts with the vault.
And in fact, in some points, they actually had
a little semi cab inside the vault
and the vault was driving around by itself.
So I would give this stunt a five.
I mean, we've all tried to go up a down escalator, right?
That's all he's doing there.
This whole stunt relies on
the person being able to run faster
than the bus is falling.
When they filmed this, the stuntperson did actually
run up the bus as it was falling.
I had some real questions, because
it's not like you're pushing off something solid.
You're pushing off something that's moving
in the other direction.
It spun around to be in exactly the right position
for him to grab the bar.
When he's holding the bar and she stops suddenly,
you get this really great example of
Newton's law of motion
where an object in motion will keep moving,
because she stops the car, and he keeps going flying around.
I would give this one a 10 for running up the bus.
I thought that was really creative and totally possible.
Again, you see a lot of tight shots,
so it does make it hard to see
what's going on necessarily.
This is a Lykan hypercar,
and it's got 780 horsepower.
This car is $3.4 million.
There's only seven of them in the world.
Sometimes I think they put it in slow motion
just so people like me
can't do the detailed calculations and mess with them.
How fast do you have to be going
so that you can span the distance between the buildings?
So, if we assume that distance is 150 feet,
you're gonna fall a little bit.
So anytime something comes off horizontally,
it's going to go down a little bit.
And you can actually see it in there,
that it probably falls about two stories,
which is roughly 20 feet.
And so the question is,
how fast do you have to be going to fall two stories
in 150 feet of horizontal distance?
If you're gonna fall two floors,
it would take just a little more than a second,
and you'd need to be going 137 miles per hour.
If you fall four floors, it would be about 1.6 seconds,
and you'd have to be going only 95 miles per hour.
Now, this car has a top speed of 245 miles per hour.
Top speed is no problem.
What is a problem, however,
is how long it takes you to get to top speed.
So, the car goes 0 to 60 miles an hour in 2.8 seconds.
In order to do that, it needs 123 feet
if you assume constant acceleration.
Those look like pretty small spaces,
because he was doing an awful lot of turning
as he was going around.
And that's only 60 miles an hour.
If you wanted to get to 125 miles an hour,
according to the specs,
that would take you 9.4 seconds.
You would need 861 feet to reach that speed,
and I don't see how you'd do that
in that tiny little tower.
And the other problem is that
when they're just driving around,
they must be pulling tremendous g-forces,
because they're driving these tiny little circles.
I tried to look up the coefficient of friction
between tires and marble, but it turns out
that it's very hard to find because most people
do not drive cars in their apartment buildings.
So I couldn't find that, but even so,
you know, I question, at going at high speed on marble,
whether he could even keep traction going around like that.
You know, again, you've got another example of,
there's a bunch of things that could happen,
and if you put them all together, you might not buy it.
Even the very strong, reinforced glass
they would use on a skyscraper like this
is not gonna stand up to a car that's 3,000 pounds
traveling at 120, 130 miles per hour.
The kinetic energy of the car is just too high.
Was he not wearing a seatbelt the whole time?
I just love the look after he does these things.
I mean, he just sort of looks like, "Oh."
I understand this Charger was especially modified
so it could drive on ice.
Obviously, the ice here is gonna be pretty thick,
but if you've got that much heat,
it's gonna melt the ice,
and that's gonna make it much harder to get traction.
The physics of how the car would move after he hit it,
that was pretty accurate.
I was pretty impressed by that.
One of the things that happens
that people don't appreciate
is when a car is on fire,
the fire quickly depletes all the oxygen.
And, you know, it's using it up,
and if you're in a car, you get very, very warm,
you get disoriented, there's smoke,
you can't see what you're doing.
And so I think, when something's on fire,
him coming out of this amount of fire,
that's got some issues with the realism, too.
I don't see any reason why this couldn't happen.
So this one I would have to give a 10.
I think this one's pretty plausible.
So, if you look up a fuel tanker that holds,
oh, I don't know, maybe 7,000 gallons of gasoline,
the density of gasoline is 6.073 pounds per gallon,
about 42,000 pounds coming toward them.
Now, if it were something doing, you know,
moving regularly, something bouncing,
that'd be fine because you could gauge it.
It's like a jump rope, where you know it's coming around,
you know to jump.
But the problem with this
is if you look how it's rolling,
it's rolling in this direction and it's rolling forward.
So there's no way you can predict
exactly how it's going to roll.
And if the tanker is 42,000 pounds
and the car is 4,000 pounds,
it's gonna squish the car.
So, my first car was a 1988 Buick LeSabre,
which is about the same size
as the 1987 Buick Grand National that you see.
The chances of it rolling over the tanker,
pretty darn slow.
When the tanker starts rolling,
it's got a certain amount of kinetic energy,
but every time it hits something,
like the wall of the canyon or the ground,
it's gonna lose some of that kinetic energy.
And that means it's not gonna bounce as high.
So actually the longer he waits,
the harder it is gonna be for him
to get his car under that tanker.
So I would give that one a three.
So, this a Nissan 350Z, I believe.
The person inside the car is actually using
a combination of the steering wheel,
the clutch, and the brakes
to make the car go around the turn.
And it turns out it's actually easier
to drift around the turn
than it is to drift in a straight direction.
I believe that this guy could probably do that,
but I'd like to know how many takes it took.
But you can drift for as long as your tires will hold out.
It's a problem because you want to have
equal traction on all four wheels.
And that means you need the same amount of weight.
When drifting, what you want is
you want the rear end of the car
to be able to slide back and forth.
When you're actually driving where the tires are rolling,
you're actually sliding those tires.
And so it's a totally different phenomenon.
At some point, you're going to do enough damage to them
that they're probably going to pop.
A good driver can definitely do that.
Now, if they would've shown the other guy,
who's just learning, doing that,
I would've given it a zero.
This is a perfect example of a static equilibrium.
So, as long as all the cars
are pulling with the same force,
Dom can't go anywhere.
And what that means is,
imagine it's just Dom and two cars,
one pulling left, one pulling right.
Those two cars are pulling with equal force.
Dom can't do anything.
The problem you have is
the traction between the tires and the ground
is what is our limiting factor here.
And they're talking about
his car having 2,000 horsepower,
3,000 horsepower, 5,000 horsepower.
I don't know if it has that much.
All it has to have
is enough horsepower to get a little bit of slack.
What he's doing, is all he has to do
is get enough slack that he can move forward,
but what I'm not understanding here is
what's happening to the forces on him from behind.
And, of course, once he gets one of them,
then you've got unbalanced force.
And the only reason this works
is because the net sum of all the forces on this car
is gonna be zero.
And once he breaks free of one, all hell breaks loose.
This only works if the people on the other side
aren't doing their job right.
We have a theory that one of the people in the other cars
momentarily lost concentration
and that must be how he got out of it.
Because that's all we could figure out
how to make it happen.
And the problem giving something like this a grade
is that you don't get to see all of it,
because you're seeing the insides of each of the cars,
and you're not seeing the overhead view.
It's really hard to see how that happened.
The doctor has to have taken that into account,
because the purpose of the cast is to immobilize the arm,
and you have to take into account
the fact that he could flex his arm, so.
Could flexing the arm break the plaster of paris?
I bet it could.
But wouldn't you assume, I mean,
maybe that's why he's always wearing sleeveless clothing.
You know, it's hard to extrapolate,
because I know I couldn't do that.
So you watch some of those things,
and you go, "Yeah, he might be able to do that."
They aren't exactly 100% true to life.
I love these movies. I think they're fun to watch.
And I think it's really great to watch something
knowing the good guys are gonna win in the end.