Fig. 61 A vehicle with passengers not wearing safety belts hits a wall.
¤ Please first read and note the introductory information and
heed the WARNINGS
The physical principles of a frontal collision are simple. Both the mov-
ing vehicle and the passenger possess energy ⇒ꢀfig. 60, which varies
with vehicle speed and body weight. Engineers call this energy “kinet-
ic energy.”
The higher the speed of the vehicle and the greater the vehicle's
weight, the more energy has to be “absorbed” in a crash.
Vehicle speed is the most significant factor. If your speed doubles (for
example, from 15 mph to 30 mph - 25 km/h to 50 km/h), the energy
increases 4 times!
Because the occupants of the vehicle in the above example are not
using safety belts, they are not “attached” to the vehicle. In a frontal
collision, they will keep moving at the same speed the vehicle was
moving just before the crash, until something stops them - here, the
inside of the passenger compartment. Because the occupants of the
vehicle in the example are not wearing safety belts, their entire kinetic
energy will be absorbed by impact with the wall ⇒ꢀfig. 61.
The same principles apply to people in a vehicle that is in a frontal
collision on the highway. Even at city speeds of 20–30 mph (30–
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 high-
er.
Of course, the laws of physics don't apply just to frontal collisions;
they determine what happens in all kinds of accidents and collisions.
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