Final answer:
The crash test dummy slams into the dashboard because it continues to move forward due to inertia, even though the car has stopped upon impact. The concept of impulse and the design of crumple zones are crucial in diminishing the forces during a collision.
Step-by-step explanation:
When the car reaches 80 kilometers per hour and then suddenly crashes into the concrete wall, the crash test dummy slams into the car’s dashboard because the car has stopped, but the crash test dummy is still moving forward. This phenomenon is due to inertia, which is the resistance of any physical object to a change in its state of motion or rest. The dummy, having been in motion with the car, will continue in motion until acted upon by an external force, which, in the absence of a seatbelt, ends up being the dashboard.
During a collision, the car's metal frame and crumple zones are designed to absorb kinetic energy and extend the time of impact. This concept is related to impulse, where an increase in the time over which a force is applied results in a decrease in the force experienced. Thus, crumple zones and airbags help to reduce injuries by spreading the forces over a longer time period.