SCIENCE JOURNAL 2018

D o W e N eed S o M uch S peed Anthony McKenna

Abstract After pondering how many deaths occur on Australian roads each year, and seeing how many of those are caused by speeding, the problem of speeding is looked into in greater detail. Kinetic Energy, as well as the braking & reaction times of cars at different speeds is looked at. Calculations are shown of both as examples, such as working out acceleration, kinetic energy, force and more. Once technological and environmental factors were contemplated in the issue, it is concluded that speeding, even by only a few extra kmh -1 , is deadly for both the people in and out of the car. Introduction Ever since the first death by car in 1869 (Byrne, 2008), automobiles have taken the lives of many. In 2017 alone, 1,225 people were killed in car accidents on Australian roads, and in December there were 25% more deaths than when compared to the last five years (Department of Infrastructure and Regional Development Australia, 2018). Of these crashes, it is estimated that speeding is involved in around 34% of them (Allianz, 2018). Based on evidence, it is clear that being over the speed limit (even by only a little) can be deadly, however, the statistics beg the questions: how does speed contribute to car accidents, and how much does going over the speed limit make a difference? Kinetic Energy and Energy Transfer In order to talk about speed’s involvement in car accidents, the workings of Kinetic Energy and energy transfer need to be explained. Kinetic energy is the energy an object has because of its motion and movement (Jain, 2009), and is measured in Joules (J). The equation for Kinetic Energy is: , where ‘K’ is kinetic energy (joules), ‘m’ is mass (kilograms) and ‘v’ is velocity (ms -1 ) (Department of Chemistry, 2017). This kinetic energy exists in cars as they move, and the

transformation & transference of that energy is a large part of what kills. As shown in Figure 1 below, the difference in Joules between speeds is quite large, and the difference gets larger in the same speed intervals as the car gets faster. For example, the difference in KE between a car travelling 50km -1 and 60km -1 is 42,337.2 J, however the difference between 90km -1 and 100km -1 is 73,280.9 J: a very large difference. For comparison, the amount of energy a car has when travelling 100km -1 , 385,780.9 J, is equivalent to about 107.16 Wh (Watt-hours) (refer to equation 7). This shows that by going over the limit even a little, the increased KE of the car can be deadly. Mentioned just before, the kinetic energy found in cars is often transferred to other forms of energy upon impact of an object. This is due to the law of conservation of energy, which states that energy cannot be created or destroyed, but rather transformed from one type to another (NeoK12, 2018). In order to know how much energy is applied to an object colliding with a car, the reaction times of drivers must be studied. Speed of car (kmh -1 ) Kinetic Energy (J) (1 dec. pl.)

Difference of Joules when compared to previous speed

50 60 70 80 90

96,450.6 138,877.8 189,034.6 246,908.6

-

42,337.2 50,156.8

57,874

312,500

65,591.4

100 73,280.9 Figure 1: Kinetic Energy increase of a car (weighing 1000kg) at increasing speeds. Refer to equation 6 for data equation example . Reactions & Stopping Time While sometimes car accidents occur at full speed, most times they happen at lower speeds, while a car is trying to slow down. However, the amount of time it takes for a car to stop depends on its speed and the driver’s reaction time, and 385,780.9

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Somerset College Journal of Scientific Issues

Year 10