Tests reveal that a normal driver takes about 0.75 s before he or she can react to a situation to avoid a collision. It takes about 3 s for a driver having 0.1% alcohol in his system to do the same. If the driver with 0.1% alcohol is travelling on a straight road at 72 km/h (20 m/s) and his car can decelerate at 1 m/s2, determine the shortest stopping distance (d) from the moment he see the pedestrians.Question 9Answera.320b.290c.260d.225
Question
Tests reveal that a normal driver takes about 0.75 s before he or she can react to a situation to avoid a collision. It takes about 3 s for a driver having 0.1% alcohol in his system to do the same. If the driver with 0.1% alcohol is travelling on a straight road at 72 km/h (20 m/s) and his car can decelerate at 1 m/s2, determine the shortest stopping distance (d) from the moment he see the pedestrians.Question 9Answera.320b.290c.260d.225
Solution
The stopping distance of a car is determined by two factors: the reaction distance (the distance the car travels before the driver reacts and applies the brakes) and the braking distance (the distance the car travels while decelerating to a stop).
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Calculate the reaction distance: The reaction time for a driver with 0.1% alcohol in his system is 3 seconds. The car is traveling at 20 m/s. So, the reaction distance is speed multiplied by time. Reaction distance = speed * time Reaction distance = 20 m/s * 3 s = 60 m
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Calculate the braking distance: The braking distance can be calculated using the formula: d = v² / (2a) where: d is the braking distance, v is the speed of the car (20 m/s), and a is the deceleration (1 m/s²). So, the braking distance is: d = (20 m/s)² / (21 m/s²) = 200 m
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Add the reaction distance and the braking distance to get the total stopping distance: Total stopping distance = reaction distance + braking distance Total stopping distance = 60 m + 200 m = 260 m
So, the shortest stopping distance for the driver with 0.1% alcohol in his system, traveling at 72 km/h, is 260 meters. Therefore, the correct answer is c.260.
Similar Questions
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