SCIENCE JOURNAL 2018

Reaction & Braking Distance Moreover, increased speed produces greater braking distances, on top of reaction distance. Speed limits are provided to prevent crashes, ensuring drivers enough time to respond/stop. Some people choose to disobey these rules, putting themselves, and surrounding people in danger. [Appendix 2] shows the consequences amid travelling at faster speeds. The two cars share like properties, however, the green car is travelling at 60km/h whilst the purple is 5km/h faster. If they happened to encounter the same hindrance ahead, the purple car would travel 2.1m further before applying the brakes (same reaction time – 1.5s: average of drivers). Although this distance seems negligible, with additional factors, it becomes crucial. After the brakes are applied, the car must then decelerate before reaching the obstacle. When moving at 60km/h, the car travels 38.9m, whereas the car travelling at 65km/h travels an extra 4.5m before stopping (The Physics Classroom , 2017). This validates that even a meagre reduction of pace dramatically minimises the risk of harm. Deceleration & Impact Speed Moreover, speeding has plausible effects on deceleration/impact speed. After activating the brakes, if the car cannot come to a complete stop before crashing, the masses will collide at the ‘impact speed’. Increased speed influences lengthier deceleration times, hence higher impact speeds. [Appendix 3] analyses how this has life-changing implications. If a car travels at 50km/h, there is enough time to decelerate before coming striking (i.e.:) a wall 45m away. Contrarily, when travelling at 80km/h, it takes almost 70m for a car to stop, by which it would have already hit the wall at 66km/h. From this, it is deduced that higher speeds suggest increased danger, as less time is obtainable to decelerate, hence, higher impact speeds.

Energy The final significant physical notion is energy. The main energy-type involved with cars is kinetic energy. When a car collides with a wall, the Law of Conservation of Energy claims that energy cannot be created/destroyed, only transformed from one form to another. This means that kinetic energy from a car’s motion is converted into heat/sound during a crash. At higher speeds, more kinetic energy is converted, thus increasing the damage. [Appendix 4] shows the formula for kinetic energy and an example of why high speeds are perilous in crashes. The 2.5KJ difference between 50ms -1 -velocity variations highlights the influence of speed on the severity of a crash. This information further establishes that driving slower means less energy in a crash and thus, less destruction. Environmental and Technological Factors Environmental Factors Forces support the physics behind environmental factors in relation to road-safety. Cars rely on forces to move/stop. One of the most significant forces, friction, occurs between car tyres and the road. Weather has large effects on the amount of friction produced, creating various hazards. In 2004, 15% of road-related accidents in NSW were caused by wet-weather (Rowland et al., 2010). After rainstorms, thin layers of water cover the surfaces of roads, decreasing resistance. This makes driving in wet-weather dangerous, declaring why cautious speeds are recommended. It is scientifically proven that wet-ness doubles stopping distances whilst icy conditions decuples this (Driving Test Success, 2018). From this, two perilous situations can ensue: aquaplaning/skidding. Both are recognised for causing numerous accidents. Aquaplaning occurs when a build- up of water between the road/surface of the car tyres results in lost contact between the two surfaces/loss of control of the vehicle. Skidding happens when tyres slip, but some traction is

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Somerset College Journal of Scientific Issues

Year 10