Impulse and Momentum in a Car Collision

PART 1: Momentum and Impulse

As modern automobiles have become more powerful and able to obtain higher velocities the need for effective safety features has become more crucial. A deeper comprehensive knowledge of the forces and processes present during collisions has led to the development of many life saving devices and smarter, more effective road design.

‘The quantity of motion of a moving body’. Oxford Dictionary, 1991

Momentum is defined as the product of an objects mass and its velocity. It is expressed by:

‘Change in momentum produced by a force’. Oxford Dictionary, 1991

An impulse is defined as the product of force and the time in which the force was applied. Impulse is expressed by:

  I = impulse

f = force

t = time

Momentum and kinetic energy are closely related. Kinetic energy is the energy an object has due to its momentum. Kinetic energy is expressed by the formula:

Low Speed Zones in Built-up Areas

Speed is one of the greatest causes of death and serious injury on Australian roads. There are several ways in which speed can increase the risk of an accident but in its relation to momentum and impulse, it is crucial in the relationship between force and energy.

From the formula:

We can see that the kinetic energy is proportion to the velocity squared which means that if the speed is doubled, the energy is quadrupled. The rapid transfer of kinetic energy is the cause of injuries in car accidents. So managing the amount of kinetic energy is crucial.

e.g. if two cars, one travelling at 50km/h and the other travelling at 60km/h crash into a brick wall. What will their energy be if both cars have an equal mass of 5000kg?

Driver 1: KE = mv2 / 2                   Driver 2: KE = mv2 / 2
                  = 5000x13.892 / 2                         = 5000x18.752 / 2
                  = 482.3 KJ                                     =878.9 KJ

This example illustrates how small...