Forces and Motion: Stopping Distances

The stopping distance of a vehicle is the sum of the thinking distance and the braking distance.
The thinking distance is the distance the vehicle travels in the time it takes the driver to react. The thinking distance increases with the speed of the vehicle.
The braking distance is the distance the vehicle travels in the time it takes to stop after the brakes are applied. This distance also increases with speed.
Factors affecting the stopping distance include speed, vehicle condition (i.e. the condition of the brakes and tyres), road conditions (wet or icy roads increase the stopping distance), and driver conditions (tiredness, alcohol, drugs or distraction can all increase the time it takes a driver to react).
When investigating forces and motion, it’s important to consider the effects of friction and air resistance. Both these forces act against the motion of the vehicle, potentially impacting stopping distance.
In physics, stopping distances are often represented graphically. The stopping distance is proportional to the square of the speed; hence, the graph of stopping distance against speed is a curve.
The Highway Code provides estimates for typical stopping distances at different speeds, but actual stopping distances can be much longer, especially in adverse conditions.
Understanding stopping distances is crucial for safe driving. The faster a vehicle is moving, the longer it will take to stop, which could lead to severe consequences in traffic situations.
Equally important is the understanding of the effect of momentum. In a collision, the vehicle and its occupants want to keep moving due to their momentum. The faster the vehicle, the greater the momentum; hence, the greater the force needed to stop it. This force can cause injury or damage.