Forces & Safety

To be able to describe why cars have safety features

Tuesday, April 18, 2023

Campaign

There has been a great deal of road safety campaigning since motorised vehicles were first invented – as far back as 1930 US physicians were urging the use of seat belts…

Audio Campaign

Visual Campaign

Visual Campaign

Visual Campaign

Task

Your task is to research car safety and produce a leaflet highlighting the key points: - Car maintenance Not driving under the influence of drink / drugs Not being distracted Knowing stopping distances Having appropriate safety features in the car (seat

belts; air bags; ABS etc…)

You need to include the relevant science in the leaflet, but it should be hard hitting, aimed at the 17-25 age range of ‘young’ drivers

Research

Useful websites: -

http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/forces/kineticenergyrev4.shtml

http://www.rospa.com

http://www.dft.gov.uk/think/

Seat Belts

Seat belts stop you tumbling around inside the car if there is a collision

They are designed to stretch a bit in a collision, increasing the time taken for the body’s momentum to reach zero, so reducing the forces on it

Seat Belts

Seat Belt History

Seat Belt History

Air Bags

Air bags have to be very rapid in operation to inflate the bag, but allow it to start to deflate before your head hits it too hard

They use the explosive decomposition of sodium azide into sodium metal and nitrogen gas that inflates the bag in around 50 milliseconds

The head is in contact with the bag for a much longer time than it would be with the dashboard, so a smaller force is exerted on the head to change its momentum

Equation

Remember: -

Force (N) = change in momentum (kg m/s)

time taken (s)

Increasing the time taken for the change in momentum reduces the overall force (so increasing the safety)

*Physicists are not worried about falling. It is the sudden stop that worries them

Safety Cars are designed to convert kinetic energy safely in a crash

– crumple zones, side impact bars, seat belts, air bags and regenerative brakes are all safety design features…

Crumple zones, seat belts and air bags all increase the impact time which decreases the force produced during the momentum change

Side impact bars help direct the kinetic energy away from passengers and into other areas of the car

Regenerative brakes use the engine to do the majority of the braking (brakes put the motor into reverse slowing the wheels and also charging the battery)

Regenerative Braking

F1 use the KERS system – this reduces the vehicles speed and charges a battery (which recovers wasted energy to be stored and used later)…