Some superheros can move faster than the wind.
The men in Apollo 10 reached
a record-breaking speed
of around 25,000 miles per hour
when the shuttle re-entered
the Earth's atmosphere in 1969.
Wouldn't we save a lot of time
to be able to move that fast?
But, what's the catch?
Air is not empty.
Elements like oxygen and nitrogen,
even countless dust particles,
make up the air around us.
When we move past these things in the air,
we're rubbing against them
and creating a lot of friction,
which results in heat.
Just like rubbing your hands together warms them up
or rubbing two sticks together makes fire,
the faster objects rub together,
the more heat is generated.
So, if we're running at 25,000 miles per hour,
the heat from friction would burn our faces off.
Even if we somehow withstood the heat,
the sand and dirt in the air
would still scrape us up
with millions of tiny cuts
all happening at the same time.
Even seen the front bumper or grill of a truck?
What do you think all the birds and bugs would do
to your open eyes or exposed skin?
Okay, so you'll wear a mask
to avoid destroying your face.
But, what about people in buildings
between you and your destination?
It takes us approximately one-fifth of a second
to react to what we see.
By the time we see what is ahead of us
and react to it -
time times velocity equals distance
equals one-fifth of a second
times 25,000 miles per hour
equals 1.4 miles
- we would have gone past it
or through it by over a mile.
We're either going to kill ourselves
by crashing into the nearest wall at super speed
or worse, if we're indestructible,
we've essentially turned our bodies into missiles
that destroy everything in our path.
So, long distance travel at 25,000 miles per hour
would leave us burning up,
covered in bugs,
and leaves no time to react.
What about short bursts
to a location we can see
with no obstacles in between?
Okay, let's say a bullet
is about to hit a beautiful damsel in distress.
So, our hero swoops in at super speed,
grabs her,
and carries her to safety.
That sounds very romantic,
but in reality, that girl will probably suffer
more damage from the hero than the bullet
if he moved her at super speed.
Newton's First Law of Motion deals with inertia,
which is the resistance to a change
in its state of motion.
So, an object will continue moving
or staying at the same place
unless something changes it.
Acceleration is the rate the velocity changes over time.
When the girl at rest,
velocity equals zero miles per hour,
begins accelerating to reach the speed within seconds,
velocity increases rapidly
to 25,000 miles per hour,
her brain would crash into the side of her skull.
And, when she stops suddenly,
velocity decreases rapidly to zero miles per hour,
her brain would crash into the other side of her skull,
turning her brain into mush.
The brain is too fragile to handle the sudden movement.
So is every part of her body, for that matter.
Remember, it's not the speed that causes the damage
because the astronauts survived Apollo 10,
it's the acceleration
or sudden stop
that causes our internal organs
to crash into the front of our bodies
the way we move forward in a bus
when the driver slams on the brakes.
What the hero did to the girl
is mathematically the same as running her over
with a space shuttle at maximum speed.
She probably died instantly at the point of impact.
He's going to owe this poor girl's family an apology
and a big fat compensation check.
Oh, and possibly face jail time.
Doctors have to carry liability insurance
just in case they make a mistake and hurt their patients.
I wonder how much superhero insurance policy would cost.
Now, which superpower physics lesson
will you explore next?
Shifting body size and content,
super speed,
flight,
super strength,
immortality,
and
invisibility.