Fig . 100 The vehicle
crashes into the wall.
The physical principles are simple. Both the vehicle and the passen -
gers possess energy wh ich varies with veh icle speed and body weight .
Engineers call th is energy "kinetic energy. "
The higher the speed of the vehicle and the greater the vehicle's
we ight, t he more energy that has to be "abso rbed " in the crash.
Vehicle speed is the most sign ificant factor. If the speed doubles
from 15 to 30 mph (25 to 50 km/h), the energy increases 4 t imes!
Because the occupants in this vehicle are not us ing safety be lts
~
page 118, fig. 99, they will keep moving at the same speed the
vehicle was moving just before the crash, unt il someth ing stops them
- here, the wall ~ fig. 100 .
The same principles apply to people sitting in a vehicle that is
involved in a frontal collis ion. Even at city speeds of 20 to 30 mph (30
to 50 km/h), the forces acting on t he body can reach one ton (2,000
lbs, or 1,000 kg) or more . At highe r speeds, these forces are even
greater .
People who do not use safety be lt s are also no t attached to t heir
vehicle. In a frontal collision they will also keep moving forward at
t he speed thei r vehicle was t ravelling ju st before the crash. Of course,
the laws of physics don't just apply to frontal coll isions, they deter-
mine what happens in all kinds of accidents and collisions . •
Safety first Vehicle OP-eration
Safety belts
What happens to occupants not wearing
safety belts?
In crashe s unbelt ed occupants cannot stop themselves
from flying forward and being injured or killed . Always
wear your safety belts!
Fig . 10 1 A driver not
wearing a safet y belt is
violent ly t hrown
forward
Fig. 10 2 A rear
pass en ge r not wearing
a safet y belt will fly
forward and st rike t he
driver
Unbelt ed occupants a re not ab le to res ist t he treme ndo us forces of
impact by ho lding tight or brac ing themselves. Without the benefit
of safety restra int syst ems, the unrestra ined occupant will s lam
violently into the steer ing wheel, instrument panel, windshield, or
whateve r else is in the way ~ fig. 101. This impact wit h the veh icle
interior has all the energy they had just before the crash.
Never re ly on airbags alone for protection. Even when they dep loy,
airbags prov ide only additiona l protect ion . Airbags a re not supposed
91>
Vehicle care Do-it-yourselt service iTechnical data
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