in today's video we're looking at stopping distance which is the minimum distance required to stop a vehicle in an emergency the first thing to know is that the total stopping distance is equal to the thinking distance plus the breaking distance and in this video we're going to look at what each of these components are and what affects them the thinking distance is how far the car travels during the driver's reaction time which is the time between the driver seeing the hazard and actually applying the brakes there are two main things that affect thinking distance the speed of the vehicle and the reaction time itself because the faster you're going and the longer the time before you brake the further your travel the reaction time will vary between different people but in general anything that decreases alertness like being tired drunk on drugs or just generally being distracted will increase people's reaction time and so increase the thinking distance breaking distance meanwhile is the distance taken to stop under the braking force which just means once the brakes have been applied under normal conditions the most important factors are the speed and mass of the vehicle as both of these increase the vehicle's kinetic energy which is going to have to be reduced down to zero in order for the vehicle to stop another factor is the condition and quality of the brakes because if these are worn or faulty they won't be able to apply as much pressure against the wheel meaning that they won't slow the car down as quickly and it will end up traveling further before it stops the other important factors relate to the traction between their car and the road for example if the road is wet or icy then there'll be less friction between the tyres and the road which can cause the car to skid or if your tyres are bold which is when they don't have any tread left then they can't grip the road as well so the condition of your tires is also really important so now that we know what affects the stopping distance we need to take a closer look at the impact of speed and for this you need to be familiar with these sorts of diagrams where we have three little green cards each traveling to the right at a different speed the purple section in each case is their thinking distance and the red section is their breaking distance so this diagram basically shows us how long it would take each of these cars to stop if they first spotted a hazard at this orange line the important thing to notice is that while the thinking distance increases proportionally with speed the braking distance increases more quickly than you'd expect in fact if you double the speed the braking distance increases four-fold and if you triple the speed it increases nine-fold this is why if we plot a graph of total stopping distance against speed it's not a straight line but rather it gets steeper and steeper as the speed increases so the take-home message is basically if you're traveling fast in a car it's going to take a lot longer to stop than you probably expect that's everything for today's video though so hope you enjoyed it and we'll see you next time you