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Assuming the weight of the driver is 70 kg, we can calculate the impact forces in two situations: Without the seatbelt, the stopping distance would be 4 cm, and the impact force is: F = 70 kg × (44.44 m/s)²/(2 × 0.04 m) = 1728 kN. With the seatbelt on, the stopping distance increases to 20 cm. The force becomes:
- Dominik Czernia
- Reaction Time
- Braking Distance
- Impact on A Pedestrian
- Impact on A Large Object
- Less Control
- Killer Speed
One reason for this increased risk is reaction time—the time it takes between a person perceiving a danger and reacting to it. Consider this example. Two cars of equal weight and braking ability are travelling along the same road. Car 1, travelling at 65 km/h, is overtaking Car 2, which is travelling at 60 km/h. A child on a bicycle—let's call him ...
The braking distance (the distance a car travels before stopping when the brakes are applied) depends on a number of variables. 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 frictional resistance between the road and the car's tyres is also important—a car with new t...
Because the pedestrian, Sam, is so much lighter than the car, he has little effect upon its speed. The car, however, very rapidly increases Sam's speed from zero to the impact speed of the vehicle. The time taken for this is about the time it takes for the car to travel a distance equal to Sam's thickness—about 20 centimetres. The impact speed of C...
If, instead of hitting a pedestrian, the car hits a tree, a brick wall, or some other heavy object, then the car’s energy of motion (kinetic energy) is all dissipated when the car body is bent and smashed. Since the kinetic energy (E) is given by E=(1/2)mass×speed2 it increases as the square of the impact velocity. Driving a very heavy vehicle does...
At higher speeds cars become more difficult to manoeuvre, a fact partly explained by Newton's First Law of Motion. This states that if the net force acting on an object is zero then the object will either remain at rest or continue to move in a straight line with no change in speed. This resistance of an object to changing its state of rest or moti...
All these factors show that the risk of being involved in a casualty crash increases dramatically with increasing speed. In the University of Adelaide study referred to earlier, this was certainly true in zones where the speed limit was 60 kilometres/hour: the risk doubled with every 5 kilometres/hour above the speed limit. A corresponding decrease...
In reality, many drivers are able to hit the brake much faster. You can use the following values as a rule of thumb: 1 second – A keen and alert driver; 1.5 seconds – An average driver; 2 seconds – A tired driver or an older person; and; 2.5 seconds – The worst-case scenario. It is highly probable that even elderly or intoxicated ...
A pedestrian hit at 30mph has a very significant (one in five) chance of being killed. This rises significantly to a one in three chance if they are hit at 35mph. Even small increases in speed can lead to an increase in impact severity. The risk of injury increases exponentially with impact speed. A crash at 30mph has twice as much energy and ...
Sep 18, 2023 · Cars, motorcycles, car-derived vans and dual-purpose vehicles can travel up to 60mph on single-lane carriageways, or 70mph on dual carriageways and the motorway. Cars which are towing can travel ...
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First, subtract the time spent at the train stops: 2.5 x 4 = 10 minutes. 2:10 minus 10 minutes leaves 2 hours of travel time. Then, apply the avg speed formula to get 120 miles / 2 hours = 60 mph (miles per hour). Example 2: A cyclist travels to and from work, covering 10 km each way.
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Feb 18, 2009 · A driver wearing a seatbelt decelerates at roughly the same rate as the car itself. Since modern cars have a "crumple zone" built into the front of the car, the car will decelerate over a distance of roughly 1.0 . Find the net force acting on a 70-kg driver who is decelerated from 21m/s to rest in a distance of 1.0m . Homework Equations
