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Sa f e ty belts
- Failure to pay attention to the warn ing light
that come on, could lead to personal injury.
Why use safety
belts?
Frontal collisions and the law of physics
Frontal crashes create very strong forces for peo-
ple riding in vehicles.
Fig. 1 55 Unbe lted occupants in a veh icle headi ng for a wall
Fig. 156 The veh icle crashes into the wall
The physical principles are simple . Both the vehi-
cle and the passengers possess energy wh ich var-
ies with vehicle speed and body weight. Engi-
neers call this energy "kinet ic energy."
The higher the speed of the vehicle and the
greater the vehicle's we ight, the more energy
that has to be "absorbed" in the crash .
Vehicle speed is the most significant fac t or. If
the speed doubles from 15 to 30 mph (25 to 50
km/h), the energy increases 4 times!
Because t he passengers of th is veh icle are not us-
ing safety belts<=> fig . 155, they will keep mov ing
at the same speed the vehicle was moving just
befo re the crash , u nti l something stops them -
here, the wall
r=>
fig. 156.
144
The same principles apply to people sitting in a
veh icle that is involved in a frontal collision . Even
at city speeds of 20 to 30 mph (30 to 50 km/h),
the forces acting on the body can reach one ton
(2,000 lbs . or 1,000 kg) or more. At greater
speeds, these forces are even higher .
People who do not use safety belts are a lso not
attached to their vehicle. In a frontal collis ion
they will also keep mov ing fo rward at the speed
their vehicle was travelling just before the crash .
Of course, the laws of physics don't just apply to
frontal collisions, they determine what happens
in a ll kinds of accide nts and co llisions .
What happens to occupants not wearing
safety belts?
In crashes unbel ted occupants cannot stop
themselves from flying forward and being in-
jured or killed. Always wear your safety belts!
Fig. 1 57 A driver not wear ing a safety be lt is violen tly
throw n forward
Fig. 158 A rea r passe nge r not wearing a safety be lt will fly
forwa rd a nd str ike the drive r
Unbelted occ upants are not ab le t o res ist t he tre-
mendous forces of impact by holding tig ht or
braci ng themselves . Without the benefit of safe -
ty restraint systems , the unrestra ined occupant
will slam violently into the steering wheel,
liJJ,-
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