Frontal collisions and the laws of physics
Fig. 1 Unbelted occupants in a vehicle heading for a brick
wall
Fig. 2 Unbelted occupants in a vehicle striking a brick wall
The physical principles involved in a frontal collision are relatively simple. Both the moving vehicle and its occupants
possess energy, which is known as kinetic energy .
The higher the vehicle speed and the heavier the weight of the vehicle, the greater the amount of energy that will
have to be released in the event of an accident.
However, the most significant factor is the speed of the vehicle. For example, if the speed doubles from around
25 km/h to around 50 km/h (15 mph to 31 mph), the kinetic energy increases by a factor of four!
The amount of kinetic energy depends on the speed of the vehicle and the weight of the vehicle and passengers. The
higher the speed and the heavier the weight, the greater the amount of energy that will be released in the event of an
accident.
Passengers not wearing seat belts are not connected to the vehicle. In the event of a frontal collision they will
continue to move forwards at the same speed at which the vehicle was travelling before impact, until something
stops them. Since the passengers in our example are not restrained by seat belts, the entire amount of kinetic energy
will only be released at the point of impact against the wall .
Even at speeds of approximately 30 km/h(19 mph) to approximately 50 km/h (31 mph), the forces acting on bodies in
a collision can easily exceed one tonne (1,000 kg). These forces are even greater at higher speeds.
This example applies not only to frontal collisions, but to all accidents and collisions.
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