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How can physics improve car safety?

Answer
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Hint: Think in terms of the forces experienced by a passenger in a vehicle upon collision or impact at high speed. Use Newton’s First Law pertaining to inertia, Second Law pertaining to the force acting on a body as the rate of change of momentum and the Third Law of action-reaction, along with the concept of impulse and change in momentum to determine how certain mechanisms are employed in a vehicle to ensure the safety of the passengers.

Complete answer:
Let us look at some of the automobile features that are employed to ensure car safety.
Crumple Zones:
The areas at the front and back of the car that are specifically designed to crumple and deform in the event of a collision are called crumple zones. When a car collides with a barrier while accelerating at a high speed, from $F=ma$ we know that it exerts a huge force on the barrier. However, from Newton’s Third law of action-reaction, the same force would be applied by the wall on the car, which would destroy the part of the car that impacted the wall. Thus, crumple zones ease the magnitude of impact by allowing for safe structural deformation. This utilizes the concept of impulse, which is the overall effect of a force acting over time. By employing crumple zones, we are essentially buying more time which reduces the force of impact.

Airbags:
Airbags are air-filled bags that are deployed in front of the passengers upon impact or crash. When a car crashes, it comes to a sudden halt while the passengers are still in a state of motion due to inertia and are subject to abrupt deceleration. The airbags increase the amount of time taken for passengers to decelerate to zero, similar to how crumple zones work.

Seatbelt:
Seatbelts are the primary means of injury prevention in motor vehicles. They basically serve to affix the passenger’s body to the car so that their body moves with the vehicle while experiencing minimal effects of inertia. This prevents the passenger’s body from moving independently of the vehicle and keeps their body in place and prevents collisions with the windshield or the back of the seat.

Headrests:
In case of a rear impact, if a passenger is wearing a seatbelt, their torso is moved rapidly forward with the car, leaving the head behind and making it bend backwards quick enough to cause an injury, usually a whiplash arising from the sudden distortion of the neck. The headrest ensures that the head moves forward at the same time and speed as the torso avoiding any untoward neck injuries.

Note:
In addition to the above features, there are other mechanisms that are employed to ensure vehicle safety. These include lowering the centre of gravity of the vehicle to prevent the vehicle from rolling over at curvy roads, adding in roll cages that prevent the roof from collapsing in case the car overturns and crashes upside down, or employing cargo barriers that fasten cargo to the vehicle so that they do not fly around or get damaged and move with the motion of the vehicle.