The stopping distance is the distance between when the driver notices the danger and when the car comes to a complete stop. This includes the thinking distance and the braking distance. So:
Stopping distance = Thinking distance + Braking distance
Thinking distance is the distance the vehicle travels during the driver’s reaction time. The reaction time is the time between when the driver sees the hazard and when they apply the brakes.
Speed is a factor which affects the thinking distance. The faster the vehicle is travelling, the further it will travel during the driver’s reaction time. This increases the thinking distance. So, a longer distance is required to brake, with the same braking force.
Although the reaction time varies between different people, Increasing the reaction time of the driver increases the thinking distance. The following factors increase the driver’s reaction time: The driver’s reaction time can increase if the driver is:
Braking distance is the distance the car travels once the driver has applied the brakes before it comes to a complete stop. The factors that affect the braking distance are:
When a force is applied to the brakes, work is done by the frictional force between the brakes and the wheels. This reduces the kinetic energy of the vehicle, transferring it to the brakes. The car’s kinetic energy decreases and the brakes’ thermal energy increases, causing it to heat up.
To stop a vehicle from travelling at a high speed, a larger braking force must be applied. However, this can overheat the brakes because more kinetic energy is transferred to thermal energy. A larger braking force can also cause the driver to lose control of the vehicle.