1.2.8 Car Safety

Objective Define thinking distance, braking distance and stopping distance, and analyse and solve problems that use these terms

Stowmarket Physics Definitions Thinking (reaction) distance is the distance travelled between the recognition of a hazard by a driver and the first application of the brakes Braking distance is the distance travelled between the first application of the brakes and the car coming to a halt

Stowmarket Physics Definitions Stopping distance is the total distance travelled between the first recognition of a hazard by the driver and the car coming to a halt. It is equal to the sum of the thinking distance and the braking distance

Stowmarket Physics Equations – thinking distance s = ut + ½at 2 but a = 0, because the brakes have not been applied, so thinking distance s t is given by s t = ut r where u = initial speed t r = thinking time

Stowmarket Physics Equations – braking distance v 2 = u 2 + 2as but v = 0, when the car comes to a rest, so braking distance s b is given by s b = u 2 / 2a where u = initial speed a= negative acceleration

Stowmarket Physics Questions OCR AS Physics Page 47 Q1 - 2

Objective Describe the factors that affect thinking distance and braking distance

Stowmarket Physics Factors affecting thinking and braking distance Thinking Distance tiredness alcohol/drugs visibility speed distractions

Stowmarket Physics Factors affecting thinking and braking distance Braking Distance road surface tyres/brakes mass of the car speed

Objective Describe and explain how air bags, seat belts and crumple zones reduce impact forces in accidents Describe how air bags work

Stowmarket Physics Project Produce an A3 poster explaining air bags, crumple zones and seatbelts, in terms of: physical principles the importance of dissipation of energy how impact forces are reduced with reference to the objectives of the Unit

Objective Describe how the trilateration technique is used in Global Positioning Systems (GPS) for cars