MOving About

Inertia is a property of matter that causes it to resist changes in velocity (speed and/or direction) (Rouse, 2005). Basically Inertia is a word we use when we talk about matter and movement (Unknown Author, Unknown Date). This idea goes all the way back to Sir Isaac Newton, a great physicist. In Newton's first law of motion it is stated that: 1 . An object at rests tends to stay in rest 2. An object in motion tends to stay in motion A great example of inertia would be if a car is driven directly into a brick wall, the car would stop because of the external force which is exerted upon by the wall.The driver requires a force to stop his body from moving forward, this can be prevented by a settable, or otherwise inertia will cause his body to keep moving forward until his body is acted upon by the same force. Newton's First Law: Newton's First Law of Motion states that â€Å"Every object continues in its state of rest or uniform motion unless made to change by a non-zero net force. â €  This law says if an object is accelerating, that is it experiencing a change on velocity, and then an unbalanced (or resultant or net) force must be acting upon it (Warren, N, 2004).From his law we can conclude that forces cause changes in motion (that is, accelerations)- they do not cause motion (Warren, N, 2004). . Newton's First Law, Image Courtesy by: Revision World Newton's first law is not apparent in real world situations because there are usually too many external forces acting upon objects on the Earth's surface. Common experience does not always seem to be in agreement with this law (Warren, N, 2004). A driver of a car on a level road for example, still needs to press the accelerator to move at a constant speed (Warren, N, 2004). Why does the car not accelerate?The season, of course, is that friction exists between the car and the road (Warren, N, 2004). Hence the forces in this case are balanced and so the law is valid (Warren, N, 2004). To accelerate the car, we ne ed to apply an unbalanced force, that is, press the accelerator more (Warren, N, 2004). Low Speed zone, Road Rules and Safety devices: In recent years many local councils have introduced lower speed limits and placed speed humps in streets to reduce the speed of cars (Warren, N, 2004). Evidence shows, and physics dictates, that slower moving cars cause less damage to occupants if a crash results (Warren, N, 2004).The speed humps makes it difficult for drivers to speed since they would damage their cars if they hit humps too fast (Warren, N, 2004). Low Speed zones are in place because, the lower your velocity, the less momentum you have and the quicker you can stop (Unknown Author, 2007). Low speed zones keep the risk of major damage to a minimum by decreasing the momentum of cars (Indri, U, 2011). Momentum increases with both velocity and mass, as shown in the equation (Indri, U, 2011). It is important to keep momentum low because in the equation, as the momentum (P) increases, so d oes the impact force (F) (Indri, U, 2011).Therefore lower speed zones also allow for a shorter stopping distance, reducing speed decreases the chance of a collision to take place, by decreasing the stopping distance and lowering momentum (Indri, U, 2011). Modern cars are built with many safety devices including: 1 . Seat Belts 2. Airbags 3. Crumple Zones Each of these devices works by effectively increasing the over which passengers are brought to rest in the event of collision (Warren, N, 2004). Air Bags and Crumple Zones both increase the stopping distance of a vehicle.Relating back to Impulse = Force X Distance, If the distance is increased, the force is lower, this reduces the ores put on the vehicle, and the occupants inside it (Unknown Author, 2007). Seat Belts: (Explain in terms of inertia) In 1948 Tucker cars became the first car company to include seat belts, prior to which even minor motor vehicle accidents could cause serious injury (Marshal and Gibson lawyers, 2012). In 1968, the United States was the first country in the world to make it a legal requirement that all new cars have seat belts (Marshal and Gibson lawyers, 2012).A seat belt is a safety harness designed to secure the occupant of a vehicle against harmful movement that may result from a collision (Indri, U, 2011). As part of an overall occupant restraint system, seat belts are intended to reduce injuries by stopping the wearer from hitting hard interior elements of the vehicle or other passengers and by preventing the passenger from being thrown from the vehicle (Indri, U, 2011). Most seat belts are equipped with locking mechanisms (or inertia reels) that tighten the belt when pulled fast (e. G. Y the quick force of a passenger's body during a crash) but do not tighten when pulled slowly (Indri, U, 2011). This is implemented with a centrifugal clutch, which engages as the reel spins quickly (Indri, U, 2011). Alternatively, this function may be secured by a weighted pendulum or ball bear ing: when these are deflected by deceleration or roll-over they lock into pawls on the reel (Indri, U, 2011). There are three types of inertia reel seat belts: 1. NIL-(No Locking Retractor) 2. LEER V-(Emergency Locking Retractor-vehicle sensitive) 3.LEER M-(Emergency Locking Retractor-vehicle and Webbing sensitive) Air bags: Hitcher, a retired industrial engineering technician, received a patent in 1953 for what he called a â€Å"safety cushion assembly for automotive vehicles (McCormick, L, 2006). † His U. S. Patent No. As the first prototype for today's modern airbags (McCormick, L, 2006). Hitcher designed the system to reduce injuries during emergency braking and frontal collisions, according to a story in American Heritage about his invention (McCormick, L, 2006).In that story, Hitcher recalled the inspiration for his invention: â€Å"In the spring of '52, my wife, my seven-year-old daughter, Joan, and I were out for a Sunday drive in our 1948 Chrysler Windsor (McCormick , L, 2006). About three miles outside Newport, we were watching for deer bounding across the road (McCormick, L, 2006). Suddenly, there was a large rock in our path, Just past the crest of a hill (McCormick, L, 2006). I remember hitting the brakes and veering the car to the right (McCormick, L, 2006). We went into the ditch but avoided hitting both a tree and a wooden fence (McCormick, L, 2006). As I applied the brakes, both my wife and I threw our hands up to keep our daughter from hitting the dashboard during the ride home, I couldn't stop thinking about the accident (McCormick, L, 2006). I asked myself: Why couldn't some object come out to stop you from striking the inside of the car? (McCormick, L, 2006)† When he returned home, Hitcher started sketching designs for his â€Å"safety cushion. McCormick, L, 2006)† The primary purpose of the airbag is to slow the passenger's speed to zero with little or no damage (Indri, U, 2011). The constraints that it has to work wit hin are huge (Indri, U, 2011).The airbag has the space between the passenger and the steering wheel or dashboard and a fraction of a second to work with (Indri, U, 2011). Even that tiny amount of space and time is valuable, however, if the system can slow the passenger evenly rather than forcing an abrupt halt to his or her motion (Indri, U, 2011). There are three parts to an airbag that help to accomplish this feat: 1 . Air Bag: The bag itself is made of a thin, nylon fabric, which is folded into the steering wheel or dashboard or, more recently, the seat or door. . Crash Sensors: These small pieces of electronics are designed to tell when the vehicle has been damaged in an accident (Cars Direct, 2013). They respond to several different sets of stimuli, including sudden stopping, increased pressure as pieces of the car are moved due to the force of the collision, and more (Cars Direct, 2013). A mechanical switch is flipped when there is a mass shift that closes an electrical contac t, telling the sensors that a crash has occurred (Indri, U, 2011).The sensors receive information from an accelerometer built into a microchip (Indri, U, 2011). According to an engineering study and airbag can be deploy in 55 milliseconds. 3. Inflators: Once the control unit determines there is an accident, it sends a signal to the inflator system (Cars Direct, 2013). The inflator sets off a chemical charge, producing an explosion of nitrogen gas, filling up the airbag (Cars Direct, 2013). As the airbag fills up, it bursts through the paneling that contains it and enters into the space of the car in order to protect you (Cars Direct, 2013).Thus the use of the airbag decreases the overall force that is applied on the passenger resulting in less serious injuries and thus saves lives (Indri, U, 2011). . Impact Triggers Air Bag Inflation, Image Courtesy: Stephen Ramp Crumple Zones: The concept of the crumple zone safety feature was first used by the Mercedes-Benz engineer Bella Barrens on the 1959 model Mercedes-Benz â€Å"Fantail† (Rive, M, Unknown Year). This innovation was first patented by Mercedes-Benz in the early sass (Rive, M, Unknown Year). The patent was then granted as patent number 854157, minion (Rive, M, Unknown Year).A crumple zone is an area of the vehicle that is designed to change shape on impact with another object at high speed (Graininess, E, 2008). This is in order to redistribute the force exerted on the vehicle so that the driver remains relatively unharmed (Graininess, E, 2008). This is achieved by crafting the front and rear of the vehicle from a material that is designed to bend or collapse into itself upon impact (Graininess, E, 2008). Often, engineers will have to compromise between using a material that offers too little resistance to force and too great a resistance to force (Graininess, E, 2008).The best way to reduce the initial force in a crash with a given amount of mass and speed is to slow down the deceleration (Indri, U , 2011). You've seen this effect for yourself if you've had to slam on your brakes for any reason (Indri, U, 2011). The forces you experience in an emergency stop are much greater than when you gradually slow down for a stoplight (Indri, U, 2011). In a collision, slowing down the deceleration by even a few tenths off second can create a drastic reduction in the force involved (Indri, U, 2011). . The crumple zones and the passenger section of a car, Image Courtesy By:Mechanics Momentum In the equation Force = mass X acceleration (F=M x A), cutting the deceleration in half also cuts the force in half therefore, changing the deceleration time from . 2 seconds to . 8 seconds will result in a 75 percent reduction in total force (Graininess, E, 2008). Crumple zones accomplish this by creating a buffer zone around the perimeter of the car (Graininess, E, 2008). Certain parts of a car are inherently rigid and resistant to deforming, such as the passenger compartment and the engine (Grainine ss, E, 2008).If those rigid parts hit something, they will decelerate very quickly, resulting in a lot of force (Graininess, E, 2008). Surrounding those parts with crumple zones allows the less rigid materials to take the initial impact (Graininess, E, 2008). The car begins decelerating as soon as the crumple zone starts crumpling, extending the deceleration over a few extra tenths of a second (Graininess, E, 2008). The fundamental idea is that it takes force to damage them. Crumple zones spend as much force as possible so that other parts of the car as well as the occupants don't suffer the effects (Indri, U, 2011).Effectiveness of Safety Devices: Seat Belts: Wearing a seat belt is one of easiest ways of protecting drivers and passengers when traveling in a vehicle (Western Australia Government, 2014). Seat belts protect vehicle occupants by decreasing the time it takes them to come to a stop in a crash, spreads the impact force over a greater area of the body, minimizes contact wi th the interior of the vehicle and helps stop them from being ejected from the vehicle (Western Australia Government, 2014). Failure to wear a seat belt contributes to more fatalities than any other single traffic safety-related behavior (Indri, U, 2011). % of people killed in accidents are not wearing seat belts (Indri, U, 2011). Wearing a seat belt use is still the single most effective thing we can do to protect ourselves in case of an accident (Indri, U, 2011). . Seat Belts, Image Courtesy By: Tableaus Seat belts are the most effective safety devices in vehicles today, estimated to save 9,500 lives each year (Indri, U, 2011). Yet only 68 percent of the motor vehicle occupants are buckled. In 1996, more than 60 percent of the occupants killed in fatal crashes were unrestrained (Indri, U, 2011). . Fatalities where NV Occupant was Unrestrained, Image Courtesy By: AustralianGovernment As you can see from the graph above after 2007 number of fatalities who were unrestrained have decr eased over the year. This is because more effective laws came in and police patrol on roads also increased over the years. Our better understanding of safety of devices such as seat belts has also played a major part. Statistically, individuals who are in accidents that have manufacturer- installed airbags and who properly wear their seat belts have a better chance of making it out of a serious accident without serious injuries (Safer, 2006).Crumple Zones: In a typical crash scenario, the crumple zone effectively redistributes the force of impact on the vehicle, leaving the ‘safety cell' intact whilst the front or rear of the vehicle is completely deformed (Car Safety Systems and Unknown Date). This means that the crumple zone is working correctly (Car Safety Systems and Unknown Date). However, crumple zones are designed to work in tandem with the additional safety features of a modern vehicle, such as the airbags, settable and collapsible steering column (Car Safety Systems a nd Unknown Date). Crumple Zones, Image Courtesy sys; ‘(21968 Crumple zones allow the front of the vehicle to crush like an accordion, absorbing some of the impact of the collision and giving some off in the form of heat and sound (K-12 School Websites, 2006). The front of the vehicle effectively acts as a cushion that slows the time it takes for the vehicle to come to a complete stop, applying less force on passengers, which could help save their lives (K-12 School Web Pages, 2006).Newton's second law of motion, force = mass x acceleration, conveys that as the time it takes for an automobile to come to rest or change direction is increased, the force experienced by the automobile (and its occupants) is decreased (Erickson, Christopher, 2006). Conversely too, if the time to stop is shorter, the force experienced is greater (Erickson, Christopher, 2006). Crumple zones add time to the crash by absorbing energy (Erickson, Christopher, 2006).Air Bags: In Australia during 1997, the then Federal Office of Road Safety collaborated with UNCAP on a consumer information program comparing the injury outcome of a series of vehicle models with and without airbags (RACE, Unknown Date). The first release covered larger passenger cars that are popular with families and fleet buyers (RACE, Unknown Date). The test results showed that an airbag halves the chance of suffering a serious head injury (RACE, Unknown Date). A second series looked at the small car group which are very popular with private and first-time new car buyers (RACE, Unknown Date).Again the test results showed that an airbag at least halved the chance of suffering a serious head injury (RACE, Unknown Date). . Airbags, Image Courtesy By: Sally Dominique A recent US study has shown side airbags also to be highly effective in reducing the risk of serious injury or death, particularly those that include head protection. Previous research has shown that the installation of air bags in vehicles significantly red uces crash related deaths, but these analyses have used statistical techniques which have not been capable of controlling for other major determinants of crash survival (Barry, S, Gimping, S, O'Neill, T, 1999).Loose Objects in Cars: Every year, loose objects inside cars during crashes cause hundreds of serious injuries and even deaths (Abraham', D, Wesleyan, M, Lamar, A, 2011). Recent studies have shown that many drivers are increasing the risk of injury or death in automobile accidents by leaving items unsecured (Grubber, D, 2012). The potential angers of loose objects in vehicles are strongly associated with Newton's First Law of Motion, inertia (Cantina, 2005). For example, say a car is traveling along a straight road (Cantina, 2005).Loose objects in the auto are â€Å"acted upon† by the body, seats, or some other part of the vehicle (whatever is touching a loose object), whenever the car accelerates (Cantina, 2005). Let's say we stop the car instantaneously and turn the c ar so it faces left (Cantina, 2005). What happens to all the loose objects inside the car? They are still going to obey the First Law of Motion, and try to continue going down the straight road (Cantina, 2005). However, since the car is now both stopped and facing left, the right wall of the car is in the way of the loose objects (Cantina, 2005).At that moment everything flies towards the right wall, and the loose objects crash hard against it (Cantina, 2005). If it wasn't for seat belts, the driver and the passenger(s) would also smash into the right wall (Cantina, 2005). However despite wearing seat belts, a passenger can still feel the force that is pushing him towards the right side of the car, in this situation. If the car was extremely heavy, or was traveling at a considerable speed, then the force of the crash would be greater Cantina, 2005). This is because of Newton's second law, F=ma, the larger the acceleration or mass, the greater the force (Cantina, 2005).This makes it obvious that loose objects in vehicles are dangerous and should be placed in compartments provided (Cantina, 2005). Everything that has been explained above can be proven right by conducting a firsthand investigation. However in this investigation, one does not have to make a sharp turn or have loose objects laying around the car. One can simply place their sunglasses on the dashboard and observe its movement whenever the car turns. If the car turns right then the sunglasses will move to the left and vice versa. This is a very simple yet accurate example of inertia in the car's frame of reference.