Grade 12 Physics Concepts: Types of Collisions
Elastic Collisions
In an elastic collision, the total kinetic energy in the system is the same before and after the collision. Losses to heat and deformation are much smaller than the other energies involved, such as when two pool balls collide and go their separate ways, you can generally ignore the losses and say that kinetic energy was conserved. If 2 cars colide and are deformed, the collision is inelastic, even if you can drive away after the accident. An elastic collision could occur if 2 cars are moving very slowly and there is a rear end collision. This could occur during bumper to bumper traffic. Elastic collisions also occur during car crashes inside the car. For example, when whiplash occurs, the head hits the seat and kinetic energy is the same.
Inelastic collisions
In an inelastic collision, the collision changes the total kinetic energy in a closed system. In this case, friction, deformation, or some other process transforms the kinetic energy. Kinetic energy isn’t conserved. If 2 cars weld together after an incident, or a car looks stuck to a tree (for example) after a crash, this is an inelastic collision.
In a collision between 2 objects of unequal mass, the more massive car would drive the compartment of the lighter car backward during the crash causing a greater speed change for the lighter car and thereby more forces. That is why lighter cars offer less protection for ocupants than heavier cars.
