Part A: Research

SEATBELTS:

Seatbelts are used in almost all motor vehicles. They are made up of two flexible but strong pieces of cloth, one that goes around the waist and then a shoulder strap that starts from the waist and then goes diagonally across the chest and to the opposite shoulder. The purpose of a seat belt is to reduce the risk of the passenger moving within the vehicle in the event of a crash.

A locking system within the seatbelt mechanism locks the seatbelt from moving in the event of a sudden jolt. This stops the passenger from moving further and absorbs the kinetic energy. 

The law of inertia means that even when the car stops, the body inside will continue moving at the speed of the car, not only that, but without a restraint such as a seatbelt the internal organs will also continue to move inside the body. 

Many deaths in car accidents as caused by the heart being pierced by the rib cage 

because the passenger was not wearing a seatbelt. 

Here is a video of a seatbelt crash test:

HEAD RESTRAINTS:

Head restraints are head rests that are located in the top of most car seats. In the event of a rear impact crash the head restraint prevents whiplash injuries to the neck. A whiplash injury is when a car is hit and with the sudden stop the head of the passengers head goes flying backwards. The head restraints prevent whiplash because it is something to support behind the head in the event of a crash.

    Here is a video example of a POOR head restraint: 

CRUMPLE ZONES:

Crumple zones are the front and back of a car that have been specifically been designed to crumple and absorb the impact of a crash instead of the cabin that holds the passengers. The front and rear of cars are made of weaker materials compared to the stronger materials that the cabin is made out of. The crumple zones have been a huge part of the development of safety features on vehicles.

Here is a video demonstrating how crumple zones work in the event of a collision:

AIRBAGS:

The design of the airbag simply came from the idea of having a soft pillow for your head to fall onto in the event of a collision. The airbag is triggered by a large impact and it acts as an additional safety feature to the seatbelt because it restrains the head from hitting the dashboard and therefore preventing serious head injuries that could take place without the protection. 

Here is a slow-motion video on an airbag crash test: