Stopping Distances (AQA GCSE Physics): Flashcards
Exam code: 8463
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Define stopping distance.
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Cards in this collection (33)
Define stopping distance.
The stopping distance is the total distance travelled during the time it takes for a car to stop in response to an emergency.
Define thinking distance.
The thinking distance is the distance travelled in the time it takes the driver to react (their reaction time).
Define braking distance.
The braking distance is the distance travelled under the braking force.
Stopping distance = ______ distance + ______ distance.
Stopping distance = thinking distance + braking distance.
How does a vehicle's stopping distance change as its speed increases, for a given braking force?
For a given braking force, the greater the speed of the vehicle, the greater the stopping distance.
True or False?
Braking distance is the distance travelled while the driver is reacting, before applying the brakes.
False.
This describes the thinking distance. The braking distance is the distance travelled under the braking force, after the brakes have been applied.
On a velocity-time graph for an emergency stop, what does the area under the graph represent while the driver is reacting, before the brakes are applied?
The thinking distance.
On a velocity-time graph for an emergency stop, what does the area under the graph represent once the brakes have been applied?
The braking distance.
While a driver reacts, before applying the brakes, the vehicle continues moving at a ______ velocity.
While a driver reacts, before applying the brakes, the vehicle continues moving at a constant velocity.
True or False?
Once the brakes are applied, a vehicle's velocity on a velocity-time graph stays constant until it stops.
False.
Once the brakes are applied, the vehicle decelerates until it comes to a halt.
Define reaction time.
Reaction time is a measure of how much time passes between seeing something and reacting to it.
What is the typical range of reaction times for someone who is alert?
0.2–0.9 seconds.
In the ruler-drop method for measuring reaction time, what does Person A do?
Person A holds a 30 cm ruler vertically so the bottom end hovers over Person B's hand, then releases it unexpectedly.
In the ruler-drop method, how is Person B's reaction time recorded?
Person B closes their hand to catch the ruler as soon as they see it move. The ruler is marked level with the top of Person B's hand, giving the distance it fell.
The ______ the distance the ruler falls, the ______ the reaction time.
The greater the distance the ruler falls, the longer the reaction time.
True or False?
In the ruler-drop method, a shorter falling distance indicates a longer reaction time.
False.
A shorter falling distance indicates a shorter reaction time; a greater distance indicates a longer reaction time.
Thinking distance = ______ of the car × driver's ______ time.
Thinking distance = speed of the car × driver's reaction time.
Name three factors that increase a driver's thinking distance.
Tiredness, distractions (e.g. using a mobile phone), and intoxication (consumption of alcohol or drugs).
What is the main factor that affects thinking distance?
The car's speed.
Why do tiredness, distractions and intoxication increase thinking distance?
They increase the driver's reaction time, which directly increases the thinking distance.
True or False?
Using a mobile phone while driving has no effect on thinking distance.
False.
Using a mobile phone is a distraction, which increases reaction time and therefore increases thinking distance.
Which factor is the main determinant of a car's braking distance?
The speed of the vehicle.
Name two additional factors, besides speed, that can affect braking distance.
Vehicle condition (e.g. worn tyres or poor brakes) and road condition (e.g. wet or icy roads).
When a driver applies the brakes, what energy transfer takes place?
The kinetic energy of the car decreases and the thermal energy of the brakes increases, as the frictional force between the brakes and wheels does work on the brakes.
The frictional force that does work on the brakes acts between the ______ and the ______.
The frictional force that does work on the brakes acts between the brakes and the wheels.
Why does a greater vehicle speed require a greater braking force to stop in a given distance?
A greater braking force is needed to produce the larger deceleration required, as described by Newton's second law of motion.
What could result from very large decelerations when braking?
The brakes could overheat and/or the driver could lose control of the vehicle.
True or False?
When a car brakes, the friction that heats up the brakes acts between the wheels and the road.
False.
The friction that does work on the brakes acts between the brakes and the wheels, not the wheels and the road.
What does the work done by the brakes represent physically, as a vehicle decelerates to a stop?
It represents the kinetic energy transferred from the vehicle to the brakes.
How is braking distance related to a vehicle's speed?
Braking distance is proportional to the speed squared.
If a vehicle's speed is ______, its braking distance increases by four times.
If a vehicle's speed is doubled, its braking distance increases by four times.
What can the equation relating work done to kinetic energy be used to estimate, for vehicle braking?
It can be used to estimate the decelerating force required for a typical vehicle travelling at everyday speeds.
True or False?
The braking distance of a vehicle is directly proportional to its speed.
False.
The braking distance is proportional to the speed squared, not directly proportional to the speed.
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