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Safety
belts
- Failure to pay attention to the warning 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. 147
Unbelted occupants in a vehicle head ing for a wall
Fig. 148
The vehicle crashes 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 "kinetic energy."
The higher the speed of the vehicle and the
greater the vehicle's weight, the more energy
that has to be "absorbed" in the crash.
Vehicle speed is the most significant factor. If the
speed doubles from 15 to 30 mph (25 to 50 km/
h), the energy increases 4 times!
Because the passengers of this veh icle are not us-
ing safety belts¢ fig . 147, they will keep moving
at the same speed the vehicle was moving just
before the crash, until something stops them -
here, the wa ll
c>
fig. 148.
136
The same principles apply to people sitting in a
vehicle 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 .
Peop le who do not use safety belts are also not
attached to their vehicle. In a fronta l collision
they will also keep moving forward at the speed
their vehicle was travelling just before the crash.
Of course, the laws of phys ics don't just apply to
frontal coll isions, they determine what happens
in a ll kinds of accidents and collisions.
What happens to occupants not wearing
safety belts?
In crashes unbelted occupants cannot stop
themselves from flying forward and being in-
jured or killed. Always wear your safety belts!
Fig. 149
A driver not wearing a safety belt is violently
thrown fo rwar d
Fig. 150
A rear passenge r not wea ring a safety belt will fly
forward and strike the drive r
Unbelted occupa nts are not able to resist t he t re-
mendous forces of impact by holding tight or
bracing themse lves. Without the benefit of safe -
ty restraint systems, the unrestrained occupant
will slam violently into the steering wheel,
.,.
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