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Bumpers are made of heavy sheet metal and are mounted on the front
and rear of the car. Bumpers are bent and formed into specific shapes
in order to absorb and deliver momentum during a collision. In the
event of a collision, the bumper absorbs some of the impact, which
decreases damage to the car and its occupants. It also protects the
front of the car by diverting all of the car's momentum to the object
with which it has collided.
The bumper is mounted to the car's chassis with special impact
absorbers. These shock absorbers are often spring loaded. In slow
speed collisions, this allows the bumper to compress, and then extend
back to its original position.
All bumpers are designed to absorb the energy of the impact. They do
this through a series of valves and air chambers. Some car bumpers
have hydraulic chambers. In the event of a collision, the absorption
unit allows air and/or hydraulic fluid to pass through small
openings. Forcing the air/fluid through the valve openings absorbs
the energy from the collision.
The bumper's job is to minimize damage, primarily to the occupants of
the vehicle and to the vehicle itself. US law requires cars to pass
special crash tests at various speeds. In order to pass, the car's
damage level during the crash must be below a specific dollar level.
This protects the consumer and is also very important for keeping the
cost of automobile insurance to a minimum.
Sometimes bumpers are constructed with built-in "crumple zones."
Crumple zones are designed to absorb impact; they will flex on
impact. As the metal flexes, the action of the bending metal converts
the kinetic energy of the car into heat. Kinetic energy is the energy
an object possesses while it is in motion.
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