![]() The slope or grade of the roadway is important-a car will stop more quickly if it is going uphill because gravity will help. The braking distance (the distance a car travels before stopping when the brakes are applied) depends on a number of variables. A driver who is distracted, for example listening to loud music, using a mobile phone or has drunk alcohol may take as long as 3 seconds to react. The figure of 1.5 seconds is the reaction time of average drivers. The difference of 2.1 metres might seem relatively small, but combined with other factors it could mean the difference between life and death for Sam. In those few moments, Car 1 travels 27.1 metres and Car 2 travels 25.0 metres. The drivers both see the child at the same time and both take 1.5 seconds before they fully apply the brakes. A child on a bicycle-let's call him Sam-emerges from a driveway just as the two cars are side-by-side. Car 1, travelling at 65 km/h, is overtaking Car 2, which is travelling at 60 km/h. Two cars of equal weight and braking ability are travelling along the same road. One reason for this increased risk is reaction time-the time it takes between a person perceiving a danger and reacting to it. Small conditions can make a big difference to the time it takes you to stop your car, such as going a few km/hr slower or being alert on the road. For speeds below 60 km/h the likelihood of a fatal crash can be expected to be correspondingly reduced. For a car travelling at 70 km/h the risk increased fourfold. Thus, a car travelling at 65 km/h was twice as likely to be involved in a casualty crash as one travelling at 60 km/h. They found that the risk approximately doubled for every 5 km/h above 60 km/h. Using data from actual road crashes, scientists at the University of Adelaide estimated the relative risk of a car becoming involved in a casualty crash-a car crash in which people are killed or hospitalised-for cars travelling at or above 60 km/h. So we happily let the speedo hover just above the speed limit, unaware that by so doing we are greatly magnifying our chances of crashing. We figure that while the speed limit is 60 km/h the police won't pull us over if we sit on 65. Now, if it takes too long, would there be any way to artificially negate the G-forces? It seems like this would make interstellar travel (at least in a single generation) much more difficult.It may not seem like much, but driving even a few kilometres per hour above the speed limit greatly increases the risk of an accident. Of course, there would be much more 'space' to accelerate, but what i don't have time to calculate is how long would it take for a spacecraft to accelerate to half the speed of light? Keeping the G-forces in a bearable range, of course But this only accelerates the crew to 27,000 kph (not exact, just a ballpark range), where as half light speed is roughly 5,000,000 kph. On a regular rocket, Falcon 9 for example, the G-forces are around 5-ish (i think). But this would cause the issue of how fast the ship could accelerate without crushing the crew members. However, the ship couldn't accelerate instantly, for multiple reasons, so it would take longer, due to the acceleration required. This is a long time, but its short enough for a single generation of humans to get there. A spacecraft traveling at half the speed of light would take 8 years to arrive there. So it occurred to me that if humans were to ever make a half-light-speed spacecraft, (a spacecraft that travels at half the speed of light) the acceleration required to get up to that speed would crush a human if it was too fast.Īlpha-Centauri, the nearest star to our sun, is 4 light-years away.
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