Stopping Distances Flashcards
All 17 cards in this deck
Describe the ruler drop test for measuring reaction time.
One person drops a ruler between another person's open fingers; the second person catches it as fast as they can and the distance the ruler fell is measured (and converted to a time).
What is a typical human reaction time?
About 0.2–0.9 s.
Other than the ruler drop test, give one method of measuring human reaction time.
A computer-based test: the person clicks the mouse or presses a key as soon as a shape or colour appears on screen.
What is the equation for stopping distance?
stopping distance = thinking distance + braking distance
What is the thinking distance?
The distance travelled while the driver reacts, between seeing the danger and starting to brake.
What is the braking distance?
The distance travelled while the brakes are applied, from starting to brake until the car stops.
On a speed–time graph of a car stopping, which parts show the reaction (thinking) time and the braking?
The horizontal line at constant speed is the reaction time; the sloping line down to zero is the braking.
True or false? At the same speed and on the same road, a computer-controlled car that brakes automatically has a shorter stopping distance than one with a human driver.
True. The computer has a shorter reaction time, so a shorter thinking distance and less distance travelled before the brakes are applied.
How does driving faster affect thinking distance and braking distance?
Both increase, so the stopping distance increases.
Why is it safer to drive more slowly in wet weather?
A wet road means less friction between the tyres and the road, so the stopping distance is longer; a slower speed gives a shorter braking distance and reduces the chance of skidding.
Name four factors that increase a driver's reaction time.
Tiredness, distraction, drugs or alcohol, and old age.
True or false? Worn tyres and brakes that need replacing make the stopping distance shorter.
False. Worn tyres and poor brakes increase the braking distance, so the stopping distance is longer.
How does a greater vehicle mass affect stopping distance?
It increases the braking distance, so the stopping distance is longer.
Why are large decelerations dangerous?
They involve very large forces on the vehicle and the people inside, which can cause serious injury (and the brakes can overheat or the car can skid).
True or false? Alcohol only affects a driver's braking distance, not the thinking distance.
False. Alcohol increases reaction time, which increases the thinking distance and so the stopping distance.
What is an anomalous result in a set of repeated measurements, and what do you do with it?
A result that does not fit the pattern (much larger or smaller than the others); leave it out when calculating the mean.
In the ruler drop test, how does the distance the ruler falls relate to the reaction time?
The further the ruler falls before it is caught, the longer the reaction time.