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Nouas Al MandowiPhysics7-5-11Safety Feature Effectiveness"Click it or ticket" it's a phrase most of us are all too familiar with, born from the necessary law to ensure driver safety on the roadways. However, just how safe are our modern safety devices? Do they truly have a positive impact on the number of deaths or injuries in car related accidents and if so how? In the following paragraphs I shall compare the effectiveness of the most common and predominant safety devices, shared by nearly every make and model of vehicle, ranging from the most simplistic airbag to the most complex seatbelt design in order to determine what impact each has and which is the most effective.To begin with it is of the utmost importance for one to understand the basic intended function and factors correlated with seatbelt and airbag design. As an accident or collision beginsto occur the vehicle is most commonly traveling in a forward motion, often the accident occurs unexpectedly within a short distance and time span. Therefore, applying the Work-Energy principle (net work=1/2mv2final-1/2mv2 initial)we may conclude that increasing the distance andthe deceleration of the car will reduce the force of the impact (f=ma). The inverse of this is also true, the less distance the car has and the less it's deceleration the greater the impact force during the collision. This is where seatbelts and airbags come into play. The seatbelt serves as "a safety belt or strap worn in a vehicle to restrain forward motion of the occupant in the event of a collision". (Collins English Dictionary) The seatbelt is intended not to stop forward motion in theinstance of a collision but rather to allow for a restrained amount of forward movement so as to
increase stopping distance and deceleration of the individual while preventing them from colliding with hard surfaces such as the steering column, windshield, or being ejected from the vehicle. In this way the seatbelt decreases the required net force applied in an instance to stop theindividual during collision or moment of impact. There are a wide variety of designs which have been incorporated in the construction of the seatbelt over the years. The most common are the lap, sash, lap and sash combo, and the inertia reel. "The lap belt is merely an adjustable strap that goes over the waist, while the sash covers the shoulder. The flaw of each of these is that they allow for too much mobility of either the upper or lower body in an accident which could result in slipping out of the belt, thus the lap and sash belt was invented. The lap and sash belt is merely a combination of both belts and was used primarily in the 60's and 70's." (Napil) The inertia reel seatbelt is the most common and widely used seatbelt to date. These are self adjusting retractable belts which have a reel that lets out or pulls in the required amount of belt to fit snugly around the individual. In the event of a