4.15 Stopping Distances Flashcards
What is the stopping distance equation?
stopping distance = thinking distance + braking distance
What is the reaction distance?
The distance the vehicle travels in the driver’s reaction time (the time between noticing the hazard and applying the brakes).
What are the two main factors that affect reaction distance?
- Your reaction time - the longer your reaction time, the longer your reaction distance. It is affected by tiredness, alcohol, drugs and distraction
- Your speed - the faster you’re going, the further you’ll travel during your reaction time
What is braking distance?
The braking distance is the distance taken to stop once the brakes have been applied
What are the 4 main factors that affect braking distance?
-Your speed - the faster you’re going, the further it takes to stop
- The mass of the vehicle - a vehicle full of people and luggage wont stop as quickly as an empty one
- The condition of the brakes - worn or faulty brakes wont be able to brake with as much force
- How good the grip of your tyres is - you’re more likely to skid when the road is dirty or if it’s icy or wet. If your tyres are bald (they don’t have any tread left) this can lead to them skidding on top of the water
What happens when the brake pedal is pushed?
This causes brake pads to be pressed onto the wheels. This contact causes friction, which causes work to be done. The work done between the brakes and the wheels transfers energy away from the kinetic energy stores of the wheels
How can you write the equation for work done by the brakes?
braking force x braking distance = 0.5 x mass of vehicle x (speed of vehicle) squared
The faster a vehicle is going, the more energy it has in its _______ energy stores, and the more _____ needs to be done to stop it. In an emergency stop, where the ___________ braking force is applied, this means that the faster the vehicle is going before the emergency stop, the longer its ________ distance
kinetic, work, maximum, braking
What happens to reaction distance as the speed increases?
It increases at the same rate as the speed. The driver’s reaction time will stay fairly constant, but the higher the speed, the further you go in that time
What type of relationship do braking distance and speed have?
A squared relationship
What does a squared relationship between braking distance and speed mean?
If you double the speed, the braking distance increases 4-fold
Which factor affects both the thinking distance and the braking distance?
Speed of the vehicle
The faster an object is going, the more ______________ it has. A _____ is needed to change this _______________. The larger the change of momentum, or the quicker this change happens, the larger the forces on the object.
momentum, force, momentum
What happens in the event of a car crash, to do with momentum and force?
In the event of a car crash, where the momentum changes a lot in a short amount of time, the forces acting on the car and its passengers are very large
What is needed for large decelerations? (e.g. in car crashes)
Large forces
