AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
The greater the braking force the greater the deceleration of the vehicle.…
Full specification wording
Factors affecting braking distance 2: The greater the braking force the greater the deceleration of the vehicle. Large decelerations may lead to brakes overheating and/or loss of control.
Braking force produces a deceleration because force equals mass × acceleration, so a larger braking force on a given vehicle gives a larger deceleration in the opposite direction to motion.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 3 of 5
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Braking force produces a deceleration because force equals mass × acceleration, so a larger braking force on a given vehicle gives a larger deceleration in the opposite direction to motion. For example, a car of mass 1200 kg with a braking force of 6000 N has a deceleration of 5 m/s², while 12000 N gives 10 m/s². Very large decelerations transfer energy to the brakes extremely quickly, so brake discs and pads can overheat, reducing braking effectiveness. They can also cause the wheels to lock or skid, so the driver loses steering control. This is why emergency braking is hazardous and why anti-lock braking systems and safe speeds help manage deceleration.
What earns the marks
- Braking force and deceleration are directly proportional for a vehicle of constant mass, as described by force = mass × acceleration.
- A larger braking force produces a larger deceleration in the direction opposing motion.
- Rapid energy transfer during large deceleration can cause brakes to overheat and become less effective.
- Large decelerations can cause loss of control, for example through skidding or wheel lock-up.
- Calculations can use force = mass × acceleration to find deceleration from braking force and mass.
Common mistakes and how to put them right
Treating deceleration as a separate quantity unrelated to force.
Put it right by applying force = mass × acceleration with deceleration as negative acceleration.
Assuming overheating only affects the engine.
Put it right: Explain that the brakes themselves heat up as kinetic energy is transferred to thermal energy.
Believing a larger braking force always shortens stopping distance safely.
Put it right: Note that excessive force can cause skidding and loss of control.
Exam tips
- Use force = mass × acceleration and rearrange it to find deceleration when force and mass are given.
- Link large deceleration to rapid energy transfer and the risk of brake overheating.
- Mention loss of control through skidding or wheel lock-up as a separate consequence of very large deceleration.
Try the lesson
The start of the Factors affecting braking distance 2: The greater the braking force the greater the deceleration of the vehicle. Large decelerations may lead to brakes overheating and/or loss of control. lesson, made from checked teaching notes for this specification point.
Have a go first
A car is braking. What happens to the deceleration of the car when the braking force is increased?
Listen
Braking force produces a deceleration because force equals mass × acceleration, so a larger braking force on a given vehicle gives a larger deceleration in the opposite direction to motion. For example, a car of mass 1200 kg with a braking force of 6000 N has a deceleration of 5 m/s², while 12000 N gives 10 m/s². Very large decelerations transfer energy to the brakes extremely quickly, so brake discs and pads can overheat, reducing braking effectiveness. They can also cause the wheels to lock or skid, so the driver loses steering control. This is why emergency braking is hazardous and why anti-lock braking systems and safe speeds help manage deceleration. A strong answer earns marks for these points. Braking force and deceleration are directly proportional for a vehicle of constant mass, as described by force = mass × acceleration. A larger braking force produces a larger deceleration in the direction opposing motion. Rapid energy transfer during large deceleration can cause brakes to overheat and become less effective. Large decelerations can cause loss of control, for example through skidding or wheel lock-up. A common slip: Treating deceleration as a separate quantity unrelated to force. Instead, applying force = mass × acceleration with deceleration as negative acceleration. Exam tip: Use force = mass × acceleration and rearrange it to find deceleration when force and mass are given.
Key words
Say what each word means before you turn the card.
Braking force
Try answering aloud or in your head before turning the card.
Deceleration
Try answering aloud or in your head before turning the card.
Overheating
Try answering aloud or in your head before turning the card.
Loss of control
Try answering aloud or in your head before turning the card.
See every definition
- Braking force
- A larger braking force produces a larger deceleration in the direction opposing motion.
- Deceleration
- A larger braking force produces a larger deceleration, and deceleration can be treated as negative acceleration.
- Overheating
- Rapid energy transfer during large deceleration can cause brakes to overheat and become less effective.
- Loss of control
- Large decelerations can cause loss of control, for example through skidding or wheel lock-up.
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Factors affecting braking distance 2: The greater the braking force the greater the deceleration of the vehicle. Large decelerations may lead to brakes overheating and/or loss of control.
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge