How exactly
do airbags save lives during a vehicle collision?
To find out, you'll need to understand momentum and impulse.
Let's explore the science behind this life saving device
and how that science relates to life on the International Space Station.
Let's go!
Hi, I'm ESA astronaut Andreas Mogensen.
In the microgravity environment aboard the space station,
even though we appear to be weightless, momentum still exists
because it depends on an object's mass and velocity.
An object's mass doesn't change whether it's in space or on earth.
We regularly monitor our own mass
on the space station to support ongoing health research.
In microgravity, we can't.
weigh ourselves on a traditional scale.
The space linear acceleration mass measurement
device is one tool on station that can help measure our mass using
momentum.
To define momentum, we use this equation:
where p or momentum is equal to mass times velocity.
We can see any object with mass that is moving is considered to have momentum.
Impulse, on the other hand, is equal to the change
in momentum of an object.
Now, about that air bag question.
In the event of a vehicle collision, an air bag
decreases the amount of force exerted on the human body by increasing
the amount of time it takes for the body to slow to a stop,
resulting in fewer catastrophic injuries
and more lives saved.
For example, I have an inflatable globe that is initially stationary.
If I apply a net force to that globe
I am causing a change to its velocity, which is thereby changing its momentum.
During the time I applied the net force, the Globe experienced an impulse.
This can also be defined as force times the amount of time for which the force
was applied.
Okay, here goes.
I'm going to gently set this globe in motion so that it hits
this firm rigid surface that I'm standing on.
Did you notice how fast that collision happened?
It was almost instantaneous.
In other words, the time from when the Globe made initial contact
with the surface to when it came to rest and then suddenly changed
directions, happened during a very small amount of time.
If we were to look at the impulse equation,
you'd notice that time and force have an inverse relationship.
This means if one variable decreases, the other must increase.
In this case, the small amount of time caused a large force
to be exerted on the globe.
Let's try a different scenario where we have a loose
curtain set up to catch the globe instead of a hard wall.
Once again, I'm going to set this globe into motion
by gently pushing it towards the curtain in this case
so that it is moving at roughly the same speed as before.
Notice that it took more time for the Globe
to come to rest after its initial contact with the curtain.
Remember that time and force are inversely proportional,
meaning that when a collision occurs over a larger increment of time,
the globe experiences a smaller force when compared to the earlier
rigid surface demonstration.
Hey, Space Center, Houston,
catch this and try it yourself.
Nice throw.
I know which case I'd prefer if I was in a car accident.
We enjoyed having you with us to learn a bit
more about the relationship between impulse and momentum.
Can you think of another situation back on earth where the Momentum Impulse
Theorem could be used to test out what you've learned today?
Try the corresponding classroom connection activity that you can find at NASA
dot gov slash stemonstrations.
Thanks for exploring physics with us today.
See you again soon!