P5 Stopping Distances (page 214) Flashcards
In an emergency (e.g. a hazard ahead in the road), a driver may perform what? to stop?
an emergency stop
When an emergency stop is performed what happens once you hit the breaks? explain your answer.
the maximum force is applied by the breaks in order to stop the car in the shortest possible distance.
(the longer it takes to perform an emergency stop, the higher the risk of crashing into whatever’s in front).
The distance it takes to stop a car in an emergency is called what?
the stopping distance.
how is the stopping distance found?
stopping distance = Thinking Distance + Breaking Distance. (see picture 1 on page 214).
What is meant by ‘Thinking Distance’?
thinking distance is how far the car travels during the driver’s reaction time. (the time between the driver seeing a hazard and applying the breakes).
What is means by ‘Breaking Distance’?
breaking distance is the distance taken to stop under the breking force (once the breakes are applied).
What are typical ‘car’ breaking distances?
14 m at 30 mph
55 m at 60 mph
75 m at 70 mph
What is ‘Thinking Distance’ affected by?
its affected by your speed - the faster you’re going the further you’ll travel during the time you take to react.
Your ‘reaction time’. - the longer your reaction time (see p.215), the longer your thinking distance.
What is ‘Breaking Distance’ afftected by?
Your speed
The weather or road surface
The condition of your tyres
how good your breaks are
Why would ‘your speed’ affect breaking distance?
the faster a vehicle travels, the longer it takes to stop.
Why would ‘the weather or road surface’ affect breaking distance?
if it is wet or icy, or there are leaves or oil on the road, there is less grip (and so less friction) between a behicle’s tyres and the road, which can cause tyres to skid.
Why would ‘the condition of your tyres’ affect breaking distance?
if the tyres of a behicle are bald (they don’t have any tread left), they cannot get rid of water in wet conditions. This leads them skidding on top of the water.
Why would your breakes affect the breaking distance?
if brakes are worn or faulty, they won’t be able to apply as much force as well-maintained breakes, which could be dangerous when you need to brake hard.
You need to be able to describe the factors affecting stopping distance and how this affects safety - especially in an emergency.
give example of the factors affecting stopping distances?
icy conditions - increase the chance of skidding (and so increase the stopping distance) so driving too close to other cars in icy conditions is unsafe.
so the longer your stopping distance, the more space you need to leave in front in order to stop safely.
When the brake pedal is pushed, what do this cause the brakes to do? explain
this causes the brake pads to be pressed onto the wheels. This causes friction, which causes work to be done. The work done between the brakes and the wheels transfers energy from the kinetic energy stores of the wheels to the thermal energy stores of the brakes. The brakes increase in temperature.
