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48
Safety
Head-on collisions and the laws of
physics
Fig.24 A driv
er not wearing a seat belt may be
thrown forward violently.
Fig.25 Any r
ear seat occupants not wearing
a seat belt may be thrown forward violently,
hitting the driver who is wearing the seat belt.
The eects of the l
aws of physics in the case of
a head-on collision are easy to explain: the mo-
ment a vehicle starts moving, a type of energy
called “kinetic energy” starts acting on both the
vehicle and its passengers.
The amount of “kinetic energy” depends on the
speed of the vehicle and on the weight of the
vehicle and of its passengers. The higher they
are, the more energy there is to be “absorbed”
in the event of an accident.
The most significant factor, however, is the
speed of the vehicle. If the speed doubles from
25 km/h (15 mph) to 50 km/h (30mph), for
example, the corresponding kinetic energy is
multiplied by four.
Given that the passengers of the vehicle in our
example do not have their seat belts fastened,
in the event of a collision the entire amount of
the passengers' kinetic energy will be only ab-
sorbed by the mentioned impact.
Even at speeds of 30 km/h (19 mph) to 50 km/h
(30 mph), the forces acting on bodies in a colli-
sion can easily exceed one tonne (1000 kg). At
greater speed these forces are even higher.
Vehicle occupants not wearing seat belts are
not “attached” to the vehicle. In a head-on col-
lision, they will move forward at the same speed
their vehicle was travelling just before the im-
pact. This example applies not only to head-on
collisions, but to all accidents and collisions.
Even at low speeds the forces acting on the
body in a collision are so great that it is not pos-
sible to brace oneself with one's hands. In the
event of a head-on collision, vehicle occupants
not wearing a seat belt will be thrown uncon-
trollably forward and will collide, for example,
against the steering wheel, instrument panel or
windscreen ›››Fig.24.
It is also important for rear passengers to wear
seat belts properly, as they could otherwise be
thrown forward violently through the vehicle in-
terior in an accident. If a rear seat occupant
is not wearing a seat belt, they are not only en-
dangering themselves but also the occupants
of the front seats ›››Fig.25.
Fastening and unfastening the seat
belt
Fig.26 Insert the l
atch plate of the seat belt
into the buckle.
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