SEKOLAH MENENGAH KEBANGSAAN DATUK MANSOR

SAFETY FEATURES IN VEHICLE

NAME: R.SRI HAARAN S/O M.RAMESHFORM: 4 HYEAR: 2015T. NAME: MR. KOH CHIN TONG

SAFETY FEATURES OF THE VEHICLE

The purpose of the site is to display how physics is involved in automobile collisions and how physics can and has been used to prevent injuries in collisions.

The aspects that are primarily being dealt with are things such as seatbelts, airbags, headrests and all.

SEAT BELT The job of the seatbelt is to hold the passenger in place so the passenger is almost part of the car which prevents the passenger from flying forward as the car stops abruptly in thecase of a collision.

When a car stopssuddenlydue to a collision with another object such as another car, a tree, pole, guardrail, etc. the car'saccelerationdecreases very quickly in a short period of time. This is calleddeceleration.Newton's Law of Inertiaexplains how this happens.

LAW OF INERTIA: An object in motion continues in motion with the same speed and direction unless acted upon by an unbalanced force. As the car collides with another object, the other object provides the forcewhich changes thespeedanddirection. The car stops going in the direction it was going in, and in some cases bounces back depending how hard of a force hits it or how muchmomentumthe car had. Also, the speed decelerates quickly due to the impact. When all this happens the passenger is not being acted upon by a force to slow them down. This part is where the seatbelt comes into play. As the person continues in their same direction and speed (forward and the same speed that the car was going) the seatbelt catches them, holding them back from flying through the air. The alternative is to not wear a seatbelt, but a force will still have to act on the person in order to slow them down. This force will come from the dashboard or windshield as the person crashes into it causing a lot of damage to themselves. A seatbelt has two parts. The first part rests over the passengers pelvis and the second part rests over the shoulder and across the chest. When the car stops abruptly the seatbelt applies thestopping forceacross a large section of the body so the damage is reduced. Seatbelts are made of flexible materials which have more give thena dashboard or windshield would have.

AIR BAGS The purpose of an airbag is to help the passenger in the car reduce their speed incollision without getting injured. Objects in a car have mass, speed and direction. If the object, such as a person, is not secured in the car they will continue moving in the same direction (forward) with the same speed (the speed the car was going) when the car abruptly stops until a force acts on them. Every object hasmomentum.Momentum is the product of a passengers massandvelocity(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. An airbag provides a force over time. This is known as impulse. The more time the force has to act on the passenger to slow them down, the less damage caused to the passenger. There is a restricted amount of time that the airbag has to act between when the car hits the other object and the passenger hits the steering wheel. About 15 to 20 milliseconds after the collision occur the crash sensors decide whether or not the collision is serious enough to inflate the airbag (usually 6 - 10 km/h). If the crash sensors decide to inflate the airbag it will be deflated at about 25 milliseconds after the crash. It takes about 20 milliseconds to inflate the airbag for the person to land into. Around 60 milliseconds the person has made contact with the airbag and the airbag now starts to deflate. The passenger continues to be acted on by the airbag as it is in the deflation process which takes about 35 to 40 milliseconds. It is still necessary to wear a seatbelt although all automobiles must be equipped with an airbag because of a few reasons: The crash sensors do not signal for the airbag to inflate unless the vehicle is moving at least 6 km/h. Damage can still occur to the passenger if the collision is of a slower speed. This is where the seatbelt plays an important role. The airbag located in the steering wheel does not help the passenger in a collision where another car hits them side on. When the car the passenger is in is backing up and collides that its rear end with another object the airbag does not help. With today's technology other airbags are being introducedin addition to the steering wheel airbag and the passenger airbag. Such airbags that are being introduced are side airbags and head airbags. HEADRESTS Headrests are found in every type of car to prevent neck injuries that occur during an automobile collision. The way the neck becomes injured due to physics. In some collisions when the car slams into another object or thebrakes are slammed on very quickly the body stays in the same position but the head is thrown either backwards or forwards. Once the head is thrownone wayit naturally is thrownthe other waybecausethe neck muscles and vertebrae force it that way. As the neck is thrownin the second directionit goes at a higher speed then when it was throwninthe first directiondue to Newton's Laws.

With & without Headrest

CRUMBLE ZONE

During a collision, slowing down the braking by even a few percent of a second can reduce the amount of force involved.

Crumple zones accomplish this by making a barrier around the perimeter of the car. This barrier serves as protection by using certain parts of the car resistant to deforming such as the passenger compartment and engine. If those unbending parts hit something, they will decelerate very quickly, resulting in a lot of force.

By making those parts surrounded by crumple zones, it allows the unbending materials to absorb the initial impact.

The car begins to slow down as soon as this area crumples.

ANTILOCK BRAKE SYSTEM (ABS)

ABSis an abbreviation for Anti-lock Braking System. It was designed to help the driver maintain some steering ability and avoid skidding while braking.

ABSwas introduced in the mid -1980s and has become "standard" equipment on the majority of vehicles sold in Canada.ABSin cars and most multi-purpose vehicles (MPVs) and pick-up trucksworks on all four wheels. This promotes directional stability and allows steering while maximizing braking.

ABSuses wheel speed sensors to determine if one or more wheels are trying to lock up during braking. If a wheel tries to lock up, a series of hydraulic valves limit or reduce the braking on that wheel. This prevents skidding and allows you to maintain steering control.

SHATTER-PROOF WINDSCREEN

Shatter-proof glassis used so that it will not break into small pieces when broken.

This may reduce injuries caused by scattered glass.

PADDED DASHBOARD

Cover with soft material.

Padded dashboardwill increase the time required to stop your head from moving forward during an accident.

The increased stopping time results in a smaller force being applied to the person's head.

Algebraically we can see that the force 'F' is inversely proportional to the stopping time.

ANTI INTRUSION BEAM When a crash results from a side impact, door beams can help protect passengers. Side impact door beams can be made of steel or aluminum. Steel door beams result in a heavier vehicle, making for a more stable frame for the car. However, heavier cars also use more fuel to operate and are therefore being replaced by aluminum beams. Aluminum beams provide the same type of safety feature with less weight making the vehicle more fuel efficient and lightweight.

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