Section 1 of 7Thinking & Braking Distances
Core Concept
- Core Concept Fundamental principles, definitions, and physical or chemical laws governing this topic.
Mechanism & Behavior
- Mechanism & Behavior Key interactions, structural properties, and process dynamics observed in experiments.
Exam Applications
- Exam Applications Quantitative relationships, key formulas, and criteria required by specification mark schemes.
Section 2 of 7Stopping Distance
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The car travelled 14 metres whilst the driver was reacting to the incident in front of him
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What was the braking distance? A
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Determine (a) The braking distance of the car
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(b) The driver's reaction time
Section 3 of 7Reaction Time
Reaction Time
Measuring reaction
- Measuring reaction Measuring Reaction Time The reaction time is defined as: A measure of how much time passes between seeing something and reacting to it The human reaction time for someone who is alert - i.e
Reaction time
- Reaction time is particularly important in stopping distance as the sum of thinking distance and breaking distance
However, human
- However, human However, human reaction time is also a common source of error in many investigations, particularly when a stopwatch is used
This reaction
- This reaction This reaction time practical has come up in exam questions before,
- so make sure you can describe the process.
- (this is an easy one to practice at home)
- so make sure you can describe the process.
Section 4 of 7Factors Affecting Thinking Distance & Reaction Time
Using a
- Using a using a mobile phone) Intoxication (i.e
Consumption of
- Consumption of consumption of alcohol or drugs) Since these factors can affect the driver's reaction time, they directly affect the thinking distance Worked Example The graph below shows how the thinking distance of a driver depends on the speed of the car
(a) describe
- (a) describe (a) Describe the connection between thinking distance and speed
(b) some
- (b) some (b) Some people drive when they are tired, despite warnings against doing so
Draw a
- Draw a Draw a new line on the graph to show how thinking distance varies with speed for a tired driver
Section 5 of 7Factors Affecting Braking Distance
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Factors Affecting Braking Distance The braking distance is the distance travelled by a car under the braking force - i.e
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whilst it is slowing down The main factor affecting the braking distance of a car is its speed There are additional factors which affect the braking distance, such as: Vehiclecondition - e.g
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it transfersenergy from the car to the brakes Therefore, the kinetic energy of the car decreases and the thermal energy of the brakes increases - i.e
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The car decelerates uniformly and stops
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The mass of the car and the driver is 1500 kg, and together they have a total kinetic energy of 168 750 J
Section 6 of 7Estimating Decelerating Forces
Estimating Decelerating Forces
Use this
- Use this Use this information to estimate the braking force for a typical car
Answer
- Answer Examiner Tips and Tricks You should be able to deduce from the equation that the braking distance is proportional to the vehicle's speed
Note, this
- Note, this Note, this actually doesn't apply at very high speeds because the brakes get hot and become less effective
This reduces
- This reduces This reduces the brakingforce, causing the braking distance to increase even further.
Section 7 of 7Exam Checklist & Tips
Specification Mastery Checklist
- Key Definitions Ensure precise recall of terms and units as required by examination mark schemes.
- Equations & Formulas Double-check balanced state symbols, subscripts, and SI unit conversions.
- Common Misconceptions Verify experimental conditions, controls, and comparative trends across groups.