8.4 Moving about
Inertia is newtons first law which states an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. It is the characteristics of an object, with mass to resist motion and to stop or slow down when in motion.
Inertia is used to resist a force, resist the motion of an object, to allow specific motion etc. In the case of motor vehicles inertia is often used for example: When a vehicle accelerates, you feel as if your body is pulled back into the seat. This is because your body's inertia tends to keep it at rest, but it is being pulled forward by the seat you are sitting in, which is moving with the rest of the vehicle. When the vehicle has finished accelerating, however, you do not feel yourself being pulled into your seat because you and the vehicle are travelling at the same velocity. If the vehicle stops suddenly, you would feel yourself being pulled forward because your body wants to keep moving while the car comes to a stop. When the vehicle turns a corner, you move to the side of the car because your body wants to keep travelling in a straight line. Inertia is also used to keep people safe in cars. Seatbelts are devices that stop inertia from keeping your body in motion when the car comes to a sudden stop (as it would in a collision). If you did not wear a seatbelt in the car, your body would move forward very quickly, possibly smashing into the dashboard or through the windscreen. A seatbelt forces your body to stop with the car.

Newton’s first law is not apparent in many situations because of the friction all the time. Energy is always lost usually in heat therefore nothing is completely efficient. If we completely ignored friction the applied force should remain constant for the entire travel, thus velocity will be constant unless an unbalanced external force acts upon if, which is in real situation/friction.

Air Bags and Crumple Zones both increase the stopping distance of a vehicle. Relating back to Impulse is equal to Force Distance, if the distance is increased, the force is lower, this reduces the forces put on the vehicle, and the occupants inside it. Low Speed zones are in place because, the slower your velocity, the less momentum you have and the faster you can stop.

Airbags and crumple zones are safety devices in car to reduce injuries and fatal accidents. The purpose of an airbag is to help the passenger in the car reduce their speed in collision without getting injured. It cushions occupants during a crash and provide protection to their bodies when they strike interior objects such as the steering wheel or a window. Airbags work by contacting the person moving forward due to newtons first law (inertia of the person). The airbag compresses while applying an equal and opposite force to the person (newtons third law) but takes a longer time to collapse thus reducing impulse force acting on the person, also the ‘pressure’ on the person is reduced due to the greater area of contact of the air bag to person. Every object has momentum. Momentum is the product of a passenger's mass and velocity (speed with a direction). In order to stop the passenger's momentum they have to be acted on by a force. In some situations the passenger hits into the dashboard or windshield which acts as a force stopping them but injuring them at the same time.

Crumple zone
Crumple zone are one of the most effective innovations for safety. Also known as a crush zone, crumple zones are areas of a vehicle that are designed to deform and crumple in a collision. This absorbs some of the energy of the impact, preventing it from being transmitted to the occupants. Keeping people safe is the primary reason why automotive engineers designed crumple zone system. In terms of momentum, crumple