Edexcel IGCSE Physics 复习笔记 1.2.6 Stopping Distance

• The stopping distance of a car is defined as:

The total distance travelled during the time it takes for a car to stop in response to some emergency

• It can be written as an equation involving two distances:

Stopping distance = Thinking distance + Braking distance

• Where:
  • Thinking distance = the distance travelled in the time it takes the driver to react (reaction time) in metres (m)
  • Braking distance = the distance travelled under the braking force in metres (m)
  • Stopping distance = the sum of the thinking distance and braking distance, in metres (m)

   

• For a given braking force, the greater the speed of the vehicle, the greater the stopping distance

ANSWER:  C

Step 1: Identify the different variables

• • Stopping distance = 40 m
  • Thinking distance = 14 m

   

Step 2: Rearrange the formula for stopping distance

Stopping distance = Thinking distance + Braking distance

Braking distance = Stopping distance – Thinking distance

Step 3: Calculate and identify the correct braking distance

• • Braking distance = 40 – 14 = 26 metres
  • Therefore, the answer is C

   

• There are various factors which can affect a vehicle's stopping distance. These are:
  • Vehicle speed - the greater the speed, the greater the vehicle's braking distance will be (because the brakes will need to do more work to bring the vehicle to a stop)
  • Vehicle mass - a heavy vehicle, such as a lorry, takes longer to stop
  • Road conditions - wet or icy roads make it harder to decelerate
  • Driver reaction time - a driver's thinking distance depends on their reaction time. Being tired, or intoxicated (i.e. alcohol, or drugs) can increase reaction time