Car Safety

Vehicle bumpers

Give way in low-speed impacts which helps increase impact time

This reduces impact force as it is spread out over a longer time period with same change in momentum

However for high speed collisions the force will be to great and the bumper/vehicle chassis will most likely become damaged

Crumple Zones

Engine compartment designed to give way when car collides head on

As the engine compartment crumples the impact time is increased and impact force is reduced, as same change in momentum as momentum is always conserved but greater time period

Seat-belts

Restrain person from colliding with dashboard or other part of the car if the car crashes or stops suddenly

The restraining force is less than the impact force would be so safer

The wearer is also stopped in a longer time frame, which means that the force on the pseron is less

Collapsible steering wheel

While the seatbelt is effective, if the driver makes contact with steering wheel can still do lot of damage

Collapsible steering wheel means that when the driver hits the wheel a lot of the force is used deforming the wheel, which reduces the force exerted by the wheel on the driver

Airbags

Reduces the force on person as the airbag acts like a cushion by increasing the impact time so reducing the force

Also, a greater contact area spreads the force out as surface area of airbag much greater than seatbelt - this reduces pressure on person

Also reduce the deceleration of the person - using F = ma as mass is constant this reduces the force

As in a crash all the kinetic energy is lost, without a seatbelt the kinetic energy of the person will be dissipated over much shorter distance and time period which greatly increases the force

Absorb energy during the crash to stop it being transferred to people within car, and also prevents direct deformation within the passenger cabin