Stopping distance = braking distance + thinking distance
Stopping distance is the distance the vehicle travels to safely come to a stop after the driver has spotted a hazard.
Thinking distance is the distance the vehicle travels during the drivers reaction time.
Braking distance is the distance a vehicle travels once the brakes have been applied.
For a given braking force the greater the speed of the vehicle, the greater the stopping distance.
Thinking distance is proportional to the speed of the vehicle.
Braking distance is not proportional to speed but is proportional to speed squared.
Reaction time
The reaction time can vary from person to person ranging from 0.2s to 0.9s
Reaction time can be affected by drugs, tiredness, alcohol or distractions.
Ways to measure reaction time:
computer - A computer is used to time how long someone takes to respond to sound or image on a screen
Ruler drop test - The ruler is dropped between someones fingers and the distance it falls before they catch it is used to calculate reaction time
Factors that affect thinking distance :
speed of vehicle
Reaction time
Reaction time can be increased by stuff like tiredness, drugs or distractions therefore increasing thinking distance.
Factors affecting braking distance :
speed of the vehicle
Mass of the vehicle
This is because they both increase the vehicles kinetic energy, which needs to be reduced to zero in order for the vehicle to stop.
Condition or quality of the brakes
This is because if they are faulty, then they wont slow the car as quickly therefore the car will travel further before it stops.
Road conditions
For example, if the road is wet or icy, then there would be less friction between the tires and the road which can cause the car to skid increasing the braking distance.
When the brakes are applied a frictional force is applied to the wheel. Work done caused energy from the kinetic energy store of the car to transfer to the thermal energy store of brakes causing the temperature of the brakes to increase.
The greater the braking force the greater the deceleration.
A large deceleration can cause the brakes over heating and the driver lose control.
answer - stopping distance includes thinking distance and a factor affecting it is reaction time, which will increase.