Seatbelts provide two main advantages in a car accident: (i)
they keep you from being thrown from the car, and (ii) they reduce
the force that acts on you during the collision to survivable
levels. The second benefit can be illustrated by comparing the net
force exerted on the driver of a car in a head-on collision with
and without a seatbelt.
(a) A driver wearing a seatbelt decelerates at the same rate as
the car itself. Since modern cars have a "crumple zone" built into
the front of the car, the car will decelerate over a distance of
roughly 1.0 m. Find the net force acting on a 61 kg
driver who is decelerated from 16 m/s to rest in a
distance of 1.0 m.
________kN
(b) A driver who does not wear a seatbelt continues to move forward
with a speed of 16 m/s (due to inertia) until something
solid is encountered. The driver now comes to rest in a much
shorter distance -- perhaps only a centimeter. Find the net force
acting on a 61 kg driver who is decelerated
from 16 m/s to rest in 1.0 cm.
__________kN