To put it simply, it’s because of newton’s first law. All objects that are in motion remain in motion unless a force is applied.

You and the car are moving. If a collision occurs, a force is applied on the car and it stops moving. But you will continue to move forward inside the car unless a force (like a seatbelt) holds you in place.

It is the law.

There are however more important reasons for wearing seat belts than just that one alone. The number one reason should be for health and safety of you and your passengers. We will give you the basic understanding of seat belts, and some reasons for using seat belts.

To understand the forces involved in a crash it is first necessary to examine how much force an object experiences as it comes to a stop. Most people feel like 50 k/h as a relatively slow speed, and may imagine that crashes at that speed are minor. But look at the physics involved in a 50 k/h crash. A 50 k/h crash exerts about 20 G’s of deceleration on the vehicle (i.e., 20 times the force of gravity). A 5 kg infant in a motor vehicle moving at 50 k/h will require at least 250 kgs of force to restrain the infant from moving forward.

Force = Body Weight x Speed

Force = 5 kgs x 50 k/h

Force = 250 kgs of restraining force is needed.

In every vehicle crash, there are actually three collisions that take place:

1. Vehicle collision(1st): When the vehicle collides with an object, such as another vehicle, a wall or tree.

2. Human collision(2nd): When the occupant moves toward the point of impact until stopped by a barrier. Unrestrained occupants collide with the interior of the vehicle, other occupants and or other unrestrained objects in the vehicle.

3. Internal collision(3rd): When the brain and internal organs move toward the point of impact, tearing connective tissue or being bruised by the collision with bones and other organs. An example of this would be the liver hitting the kidneys, or the brain hitting the front of the skull.

An injury is caused by the transfer of energy to body tissue, whether it is the energy of heat in a burn or the energy of mechanical force in a crash.

In the first collision [vehicle collision], the vehicle begins stopping as soon as it collides with a stationary object. From the time of impact, to a complete stop in a 50 k/h crash is about one-tenth of a second. As the vehicle slows, the front of the vehicle crushes, absorbing some of the energy of the impact. This known as “ride down”. A properly restrained occupant can ride down the crash (stopping with the vehicle), experiencing about the same amount of force as the vehicle.

In the second collision [human collision], a restrained occupant decreases the chances of injury during this collision because the seat belts stretch during impact, which absorbs the energy of the impact, and restrains the occupant in their seat. Sometimes the safety belts can leave bruises and sores after the impact, but they are rarely severe. An unrestrained occupant on the other hand, continues to move toward the point of impact, even though the vehicle begins to stop once impact occurs. The unrestrained occupant finally encounters an outside force (the interior of the vehicle) about the time that the vehicle has come to a complete stop or is bouncing back. As the occupant collides with the interior of the vehicle, he or she decelerates from 50 k/h to a standstill in a few hundredths of a second, much faster than did the vehicle. The unrestrained occupant may experience over 100 G’s of deceleration (compared to the vehicle’s 20 G’s). The more rigid the materials encountered and the rebound of the vehicle shorten the period of deceleration and generates higher G force. With only the occupant’s body to absorb the energy of the crash, the risk of injury is high. Ejection is very high as well.

In the third collision [internal collision], injuries could be very severe depending on the force of the impact. Even though the outer body may appear uninjured, the liver, spleen, kidneys and other organs may be torn, bruised and/or bleeding. Impacts to the head that do occur.may cause “closed head injuries” resulting from the soft tissue of the brain hitting the skull or being torn as the skull fractures. Any of these injuries may be difficult to detect immediately, yet they are often fatal

This an extremely complicated question, for which I doubt you will locate an entire answer. permit me provide you 2 examples: (the two very fair) – an extremely small motor vehicle and an extremely massive motor vehicle collide.. the small motor vehicle gets overwhelmed on an identical time as the very massive motor vehicle has some scratches on the front.. the great motor vehicle is safer. – an extremely small motor vehicle and an extremely massive one or going part by ability of part at severe speed, unexpectedly the line turns to the the appropriate option the great motor vehicle guidance over.. the small motor vehicle is safer there is not any rule for secure practices, it relies upon on the circumstances. You pronounced you needed equations… how approximately F = m * a;.. is this good adequate 🙂 ?