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. 10 5 Unbe lted occupants in a ve hicle headi ng for a wall
Fig. 106 The vehicle cras hes into the wall
The physical principles are simple . Both the vehi-
cle and the passengers possess energy which 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 . 105, 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. 106.
110
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. 107 A drive r not wea ring a safety belt is violent ly
t hrown forward
Fig. 108 A rea r passe nge r not wea ring a safety be lt will f ly
forwa rd and str ike the driver
Unbelted occupants are not ab le to res ist the tre-
mendous forces of impact by holdi ng tight or
braci ng themselves. Without the benefit of safe-
ty restraint systems, the unrestra ined occupant
will slam violently into t he stee ring wheel ,
Ill>
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