Travel Reference
In-Depth Information
independently tested to ensure that you have real, not merely cosmetic,
security. How do you know which level of protection you require and
whether the barriers you are considering have the ability to meet the
anticipated threat?
Calculating the level of impact is a matter of simple mathematics and
physics. Kinetic energy is a product of the mass (weight in kilograms) of
an object and the square of the velocity (measured in meters/second) at
which it travels divided by 2. Thus the speed at which the attacking vehi-
cle is traveling has a greater effect upon the level of impact than does its
mass. A Honda Civic hitting a barrier at 100 miles per hour has greater
kinetic energy than a cement mixer hitting it at ten miles an hour. To
make this calculation easier, we will use kilograms for mass and meters per
second for velocity. For example, the kinetic energy produced by a cement
mixer weighing 7,500 kilograms moving at 10 meters per second can be
calculated as follows:
Kinetic energy
Velocity
(meters per second) squared divided by 2
Mass (weight in kilograms)
7,500 kilograms
10 meters per second squared (100)
divided by 2
375,000 joules
In the case of a 1,000-kilogram Honda moving at 50 meters per second,
the kinetic energy is calculated as follows:
1,000 kilograms
50 meters per second, squared (2,500)
divided by 2
1,250,000 joules
As you can see, the kinetic energy produced by the lighter and faster
object produces greater kinetic energy. However, this calculation does not
tell the whole story. Remember that the kinetic energy will be converted
into heat, sound, and permanent deformation of the vehicle. In the case
of the Honda, it is quite likely that the car would virtually disintegrate
upon impact. A far more massive vehicle like the cement mixer will not.
There are several other variables that enter into this discussion, but suf-
fice it to say that controlling the speed at which a vehicle can approach
an entry point is critical to preventing a successful attack. For that reason,
most fortified entrance points are designed to require the driver to make
a relatively sharp turn before reaching the barrier, thus preventing the
attacking vehicle from attaining the same speed as it could if the truck or
