Car Design and Safety

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Regenerative Braking Systems

-when you apply the brakes, work is done
-the brakes reduce the kinetic energy of the car by transferring it into heat energy (more traditional braking systems)

Regenerative Braking Systems:
-used in some electrical and hybrid cars
-brakes --> put the vehicle's motor in reverse so the motor is running backwards and the wheels are slowed 
-the motor acts as an electric generator- it converts kinetic energy into electrical energy which is stored as chemical energy in the vehicle's battery

Advantage:
-it stores energy rather than wasting it

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Cars are designed to convert kinetic energy safely

  • If a car crashes, it will slow down very quickly 
  • ^So, a lot of kinetic energy is converted into other forms of energy in a short amount of time- dangerous for the people inside the car
  • Big change in mometum over a very short time, huge forces experienced
  • Car designs convert kinetic energy in a way that is safest for the car's occupants
  • ^increasing the time over which mometum changes happen- lessens force on passengers
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Crumple Zones

-at the front and back of the car, crumple on impact

-the car's kinetic energy is converted into other forms of energy by the car body as it changes shape

-they increase the impact time, which means the force produced by the change in mometum is decreased

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Side Impact Bars

-strong metal tubes fitted into car door panels

-they help direct the kinetic energy of the crash away from the passengers to other areas of the car, such as crumple zones 

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Seat Belts

-stretch slighly and so increase the time taken for the wearer to stop

-this reduces the forces acting on the chest 

-some of the kinetic energy of the wearer is absorbed by the seat belt stretching

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Air Bags

-slow you down more gradually

-prevent you from hitting hard surfaces inside the car 

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Cars have different power ratings

-the size and design of car engines determine how powerful they are

-the more powerful a car engine, the more energy it transfers from its fuel every second and so the faster its stop speed can be

-designed to be aerodynamic- shaped in such a way that air flows easily and smoothly past them- minimising their air resistance

-cars reach their top speed when the resistive force equals the driving force provided by the engine. So, with less air resistance to overcome, the car can reach a higher speed before this happens. Aerodynamic cars have higher top speeds 

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