Safety Features found in Cars

JohnChief-Investigator

HCI INSURANCE PTE LTD

LANG GAR! : Physics PBLTeam 8 : Wee Yong | Daniel | Hao Yuan

Crumple zone

Designed to absorb energy from impact during an accident by controlled deformation

Manage crash energy, absorbing it within outer parts of vehicle rather than being directly transmitted to occupants, while also preventing deformation of passenger cabin

Achieved by controlled weakening of sacrificial outer parts of the car, while strengthening and increasing rigidity of inner part of body of car

Crumple zone THE PHYSICS

NEWTON’S FIRST LAW

An object at rest stays at rest and an object in motion stays in

motion with the same speed in the same direction unless acted upon by an

unbalanced forceIf a vehicle is travelling at 50 mph, so are the bodies inside If this vehicle stops abruptly into a solid wall, the bodies will “feel” the need to keep going in the same direction at 50 mphEven if the bodies themselves stop, the internal organs will continue to move, thus causing severe injuries. 

Crumple zones absorb the crash energy developed during an impact,

as certain parts of the car are designed to allow deformations

Crumple zone

NEWTON’S SECOND LAW F = ma

If the time required by the vehicle to stop increases, the force experienced by the automobile and its occupants decreases 

THE PHYSICS

Crumple zones delay the collision.

Instead of having two rigid bodies instantaneously colliding,

crumple zones increase the time before the vehicle comes to a halt.

Deceleration is reduced, and the force of impact decreases.

 

AIRBAG

Occupant restraint consisting of a flexible envelope designed to inflate rapidly during a collision

cushioning the impact of collision

preventing occupants from striking interior objects such as steering wheel or window

Designed to only inflate in mild to severe frontal crashes

Airbag THE PHYSICS

 IMPULSE-MOMENTUM CHANGE THEOREM

Ft = m Δv

The greater the time over which the collision occurs, the smaller the force acting upon the object. Thus, to minimize effect of the force on an object involved in a collision, the time must be increased. When encountering a car collision, the driver and passenger tend to keep moving in accord with Newton's first law, resulting in a large force exerted over a short time in order to stop their

momentum.

 Air bags extends the time required to stop the momentum of the driver and passenger, hence minimizing the effect of the force on an object involved in a collision.

Airbag THE PHYSICS

PASCAL’S PRINCIPLEPressure exerted anywhere in a confined incompressible fluid is

transmitted equallya in all directions throughout the fluid such that the pressure ratio (initial difference)

remains the same

The airbag exerts an equal pressure on all points in contact with it. The same force is distributed over a larger area, reducing the maximum pressure on the body.

Seat Belt Safety harness designed to secure occupant against

harmful movement that result from collision or sudden stop Reduce injuries by

stopping wearer from hitting hard interior elements of vehicle ensuring wearer is in the correct position for airbag to deploy prevent passenger from being thrown from the vehicle

Absorbs energy by being designed to stretch during any sudden deceleration less speed differential between passenger's body and vehicle interior spread loading of impact on passengers body.

Seat Belt IMPULSE-MOMENTUM

CHANGE THEOREMFt = m Δv

THE PHYSICS

Seat belt holds the driver back, expelling the kinetic energy of their movement into the soft fibres. Seat belts are made of cloth and are flexible, increasing the time the body takes to slow down. Recalling impulse and momentum, increased time of impact results in lesser impact force. By slowing down more gradually the force on the body is many times less then it would be if it stopped almost instantly as it would if slamming into a rigid object.

Seat Belt THE PHYSICS

Moderate amount of stretch in seatbelt harness can extend the stopping distance and reduce average impact force on wearer.

If the belt stretched 0.5 ft in the scenario, it would reduce the deceleration to 20 g's and the average impact force to 3200 lb.

References

• http://www.money-zine.com/Financial-Planning/Leasing-or-Buying-a-Car/Car-Safety-Features/

• http://en.wikipedia.org/wiki/Crumple_zone• http://www.autoevolution.com/news/how-crumple-zones-work-7112.html• http://en.wikipedia.org/wiki/Airbag• http://www.explainthatstuff.com/airbags.html• http://www.physicsclassroom.com/class/momentum/u4l1c.cfm• http://hyperphysics.phy-astr.gsu.edu/hbase/seatb2.html• http://en.wikipedia.org/wiki/Pascal's_law• http://en.wikipedia.org/wiki/Seat_belt• http://www.ehow.com/how-does_4925504_how-seat-belts-work.html• http://autofyz6.wordpress.com/2008/04/23/the-physics-of-seat-belts/