Here we will observe here is how energy is dissipated and how the stress is transferred.
If you had studied elementary physics, you would know that there are two types of collisions, namely elastic and inelastic, and that there is an exchange or transfer of energy during collisions.
This analysis is more relevant in the automotive and aerospace industries. Making a full-size vehicle and then performing a destructive test on it again is a costly affair. Therefore, crash analysis is used there to save time and cost.
It shows the energy dissipation during the collision.