P3f: Crumple zones Flashcards
Momentum equation
momentum (kg m/s) = mass (kg) * velocity (m/s)
Force and momentum equation
force (N) = change in momentum (kg m/s) / time (s)
Use Newton’s second law of motion to explain why force = change in momentum / time (3)
any force applied to an object increases its acceleration (F = ma)
acceleration = change in velocity / time
mass * change in velocity / time = change in momentum / time
(momentum (kg m/s) = mass (kg) * velocity (m/s))
How can force/injury be reduced during a car crash? (3)
spread change in momentum over a longer period of time to decrease force
increasing collision time also decreases deceleration which reduces force
increasing stopping distance allows the vehicle to decelerate over a period of time, therefore reducing force
Forces can be reduced when stopping by:(3)
Increasing stopping/collision time (e.g. seatbelt)
Increasing stopping/collision distance (e.g. crumple zone)
Decreasing acceleration (e.g. Air bags)
Factors affecting force during car crash (3)
less time taken for change in momentum (car crash) means higher force
higher mass of car means higher force
greater change in velocity means greater change in momentum/acceleration, resulting in higher force
Describe some car safety measures(4)
Seat belts(convert kinetic energy to elastic energy)
crumple zone(absorbs some of its energy by changing shape and crumpling)
airbags(absorb some of the person’s kinetic energy by squashing up around them)
anti-locking braking system brakes(prevents accidents)
How are seatbelts, crumple zones and airbags useful in a crash(4)
absorb energy
change shape
reduce injuries
reduce momentum, to zero slowly, therefore reducing the force on the occupants
How are test data gathered
Using computer modelling or crash tests with real vehicles and dummies
Describe how ABS(anti-lock braking system) work(4)
Help drivers keep control of the car’s steering when braking hard
When a driver brakes hard (e.g. to avoid a hazard), ordinary brakes lock the wheels so they can’t turn, which can cause the car to skid
ABS automatically pump on and off to stop the wheels locking and preventing skidding
They also give the car a shorter braking distance
Advantages of using seatbelts(4)
Seat belt usage reduces the chance of traffic-related fatalities
prevents ejection from the vehicle
Wearing a seat belt minimizes the body’s contact with the interior of the car resulting in fewer injuries
Seat belts spread the force of impact over larger parts of the body reducing severity of injuries
Disadvantage of using seatbelts(4)
Seatbelt use tends to increase risk-taking in drivers and make them drive more dangerously
In many cases, the fibers of the seat belt can cause harm to the chest
It may also cause more serious damage to the internal organs
may trap the person in a fire
