Seat belts and air bags

1. MSeuI Belts
eind Air Bogs
An automobile can provide a
frightening lesson in inertia.
A person in a car traveling at
88 kmlh (55 mph) is also
traveling at 88 km/h.lf that person is
unrestrained and the car is suddenly
stopped by a wall or telephone pole, the
person will continue to move forward at
88 kmlh until stopped by the steering
wheel, dashboard, or windshield.
Automobile Safety Systems
Automotive engtneers have long been
aware of the hazards associated with trav-
eling in a car. Over time, they have
developed a number of different systems
to overcome inertia and prevent or
reduce crash-related injuries.
Newer vehicles are equipped with
head restraints. ln a rear-end collision a
passenger's head is thrown back and hits
the head restraint. This support prevents
serious injury by stopping the backward
motion of the head. Look at the photos
on the next page of other automobile
safety systems.
Reading Focus How does inertia influence the design of
automobile safety devices?
A When a car stops suddenly in a crash, inedia will
cause an unrestrained person to travel forward at the
car's original speed. The person stops when he or
she strikes the wheel, dashboard, or windshield.
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2. One of the great safety inventions of
recent decades is the air bag. Stored in
the dashboard or steering column
of a car, the bag prevents the driver from
being thrown into the steering
wheel or dashboard. )
A A combination of seaf belts, shoulder belts,
and air bags can substantially reduce injury in
a crash by overcoming inertia and stopping a
person before he or she strikes the steering
wheel, dashboard, or windshield.
INVESTIGATION I
REvIEw l. ln terms of inertia, compare a car sitting in a
driveway with a car rolling along a level street.
2. What is Newton's first law of motion?
CRITICAL 3. You bump into a table, and a glass vase on the
THINKING table tips toward you. What made the vase tip? Why
did it tip toward you and not away from you?
4.ln a head-on collision of two cars, occupants t
j f.^ first move forward and then backward. Explain.
W
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