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Newton's Laws of Motion - Seatbelts

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Jose Raphael

on 18 April 2013

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Transcript of Newton's Laws of Motion - Seatbelts

Seat belts The importance of By José Ablaza Introduction The following presentation will explain and describe the purpose of the seat belt in a car or any vehicle and how it could save your life if you ever happen to be involved in an accident. What will also be presented is how seat belts are relevant to two of Isaac Newton’s Laws. Newton's Three Laws 1. An object will remain at rest, or will not change its speed or direction, unless it is acted upon by an outside, unbalanced force (also known as the Law of Inertia). 2. The mass of an object affects the way that it moves when acted upon by one or more forces. F=ma where, F=net force (N), m=mass (kg), and a=acceleration (ms-2). 3. For every action, there is an equal and opposite reaction. What is a seat belt? A seat belt is a strong belt or strap made from synthetic materials, and secures a person to a vehicle (e.g. A car) to prevent injury. It is sometimes referred to as a safety belt. How many types of seat belts are there? There are four main types of seat belts: A two-point seat belt (also known as a lap belt). Lap belts are mainly found in airplanes, and older cars. It is called a two-point seat belt because it connects at two points; at each side of your lap.
•A three-point seat belt. This seat belt is structured in a ‘Y’ formation, and is the standard issue seat belt for most cars around the world. Because the three-point belt has a sash around your waist, and your chest, in a collision the energy of the moving body would distribute over your chest, shoulders and pelvis. It is called a three-point belt because it connects at three points; both sides of your waist, and at your shoulder. •4-6 point seat belt. These types of belts come in a variety of four, five or six points. They are mainly found in racing cars, and the four-point belt is also found in child safety seats. •Seven-point. The seven-point seat belt is only found in aerobic aircraft vehicles. It consists of a five-point belt, with two extra lap belts at each side attached to the frame of the plane itself. Lap Belt 1st point 2nd point 3-point belt 1st point 2nd point 3rd point 5 points 7-point belt How do seat belts protect you if you are involved in an accident? At the end of the seat belt, there is a little mechanism called the retractor. This device is responsible for retracting your seat belt, and locking your seat belt in the case of an incident or when you stop suddenly. The retractor mechanism is made out of a ratchet gear, a pendulum and a pawl. When the car comes to a sudden stop, a force called inertia (Newton’s 1st Law) will cause the pendulum to swing forward (just as your body would). On the other side of the pendulum is the pawl, and when the pendulum moves, the pawl will catch onto the gear, making it impossible for the seat belt to extend. By the seat belt not extending, it prevents your body from slamming into the steering wheel, or from flying out of your seat and smashing into the windshield. If you are travelling on the freeway at 100 km/h whilst not wearing a seat belt, when you suddenly collide or crash, your head will immediately bang on the windshield at 100 km/h! At that speed you will have major brain damage, if not, death! Gear Pawl Pendulum Belt Swung forward Gear catches The seat belt works in relation to two of Newton’s Laws. Newton’s 1st Law As explained previously, the seat belt locking system works because of inertia. The pendulum is stationary until the car stops, causing the pendulum to swing.
The pendulum appears to be 'still' because it is travelling at the same rate of the car. When the car comes to a sudden stop, because of the law of inertia, the pendulum continues to go, swinging forward.
Your body is the same as the pendulum. You are travelling at the same rate as the car, when the car stops, you keep going, but the seat belt stops you preventing any serious damage done to your body. Newton’s 3rd Law When you are in a collision, your body is automatically moved forward into your seat belt, but then your seat belt pushes you back. Because the third law states that ‘for every action, there is an equal and opposite reaction’, then ‘your body continuing to move forward at the car’s previous speed’ is the action, and the seat belt around you is the opposite reaction because it is pushing you in the opposed direction. (law of inertia) Your direction Seat belt http://hyperphysics.phy-astr.gsu.edu/hbase/seatb.html http://auto.howstuffworks.com/car-driving-safety/safety-regulatory-devices/seatbelt3.htm http://www.formula1-dictionary.net/Images/safety_belt_7_point.gif http://www.custom-car.us/_images/5-pointharness.jpg http://upload.wikimedia.org/wikipedia/commons/thumb/1/12/Seatbelt.jpg/220px-Seatbelt.jpg http://www.nzta.govt.nz/vehicle/choosing/features-protect/img/lapbelt-img4.jpg http://www.seattlefabrics.com/Polyester%20Seatbelt.jpg http://civic.honda.com.au/resources.ashx/GalleryItems/556/ImageFile/CE0AB47CAC9DA4E15F659F781C805BFA/civic_pretensioner.jpg bibliography http://auto.howstuffworks.com/car-driving-safety/safety-regulatory-devices/seatbelt3.htm
http://www.essortment.com/seatbelts-work-57248.html THE END newton's laws of motion
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