Good question! We need to think about what
exactly it is that harms a passenger when a car
crashes. The important thing to keep in mind is
that when a car crashed, it goes from moving
very fast to not moving at all very quickly:
this means that there's a very large
acceleration (acceleration is how quickly the
speed of something changes). It's this
acceleration that can hurt a human being.
During a car crash, a passenger without a
seat belt will fly into the front of the car and
stop suddenly; this sudden stop is where the
large acceleration that hurts the passenger
happens. The point of a seat belt is to "catch"
the passenger and slow him or her down more
slowly, decreasing the acceleration (this is
also what airbags are for). Now, if a car is
going REALLY fast, even the seat belt slows down
the passenger too quickly, and can hurt the
You might ask: what does "REALLY fast" mean?
Well, that depends on a bunch of stuff, like the
type of car, the size of the passenger, the type
of collision (head-on or side-on), and so on.
For example, you may have heard that cars
have "crumple zones" that are supposed to
crumple in a car accident to decrease the
acceleration on the passengers inside. Some
cars have very good crumple zones and can
protect passengers very well. In these cars, a
seat belt is enough to protect a passenger in
high-speed collisions. Other cars have smaller
crumple zones, so in these cars, a passenger can
be hurt by the seat belt even in lower-speed
As you might have noticed, protecting
passengers in a car can be quite complicated:
that's why car companies put their cars through
lots of crash testing to see how well a
passenger is protected in an accident.
Click Here to return to the search form.