stopping distances

• stopping distance = thinking distance + braking distance
• thinking distance: how far car travels during drivers reaction time
• braking distance: distance taken for car to stop under braking force
• thinking distance affected by: speed, reaction time, tiredness, drugs
• braking distance affected by: speed, weather/road surface, condition of tyres and brakes
• braking relies on friction between brakes and wheels
• when the brake pedal is pushed, brake pads are pressed onto wheels, this causes friction which causes work to be done. this transfers energy from kinetic stores of wheels to thermal stores of brakes
• the faster a vehicle is going, the more energy it has in its kinetic stores, so the more work needs to be done to stop it, this means that a greater braking force is needed to make it stop within a certain distance
• a larger braking force means a larger deceleration, these can be dangerous because they may cause brakes to overheat or could cause vehicle to skid
• as a car speeds up, the thinking distance increases at the same rate as speed (linear graph)
• braking distance increases faster the more you speed up, the word done to stop the car is equal to energy in cars kinetic store