# P3 - Crumple Zones

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What is the formula for momentum?
momentum = mass x velocity
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What are the units for momentum?
kgm/s
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What is the formula for force?
force = change in momentum / time
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How can the force be reduced?
Spreading the momentum change over a longer time
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How can force be educed by reducing the acceleration?
Increasing stopping or collision time, increasing stopping or collision distance
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What are some examples of safety features that do this?
Crumple zones, seat belts, air bags, crash barriers, escape lanes
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What are car safety features that absorb energy when the vehicle stops suddenly?
Brakes that get hot, crumple zones that change shape, seat belts that stretch a little, air bags that inflate and squash
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What happens for the crumple zones on impact?
At the front and rear end absorb some of its energy by changing shape or crumpling
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What happens for the seat belts on impact?
Stretch a little so that some of the person's kinetic energy is converted to elastic energy
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What happens for the air bags on impact?
Absorb some of the person's kinetic energy by squashing up around them
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What do all of these safety features do?
Absorb energy, change shape, reduce injuries, reduce momentum to 0 slowly therefore reducing the force on the occupants
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Why do some people not like seat belts?
Risk of chest injury, may be trapped in a fire, drivers encourages to drive less safely as they know they have the protection from the seat belt
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What is a primary feature which helps to prevent a crash?
ABS brakes
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What goes on in the ABS system?
Wheel-speed sensors send information to a computer about the rotational speed of the wheels. The computer controls the pressure to the brakes, via a pump, to prevent the wheels locking up. This increases braking force just before thewheelsstarttoskid
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What is kinetic energy lost equal to?
work done by the brakes
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What is the formula of braking distance x force?
Fd = 1/2 mv^2
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What happens if F increases?
D decreases
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What is cruise control?
Stops a driver becoming tired on a long journey and pressing harder on the accelerator
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What are electric windows and paddle shift control?
Allow the driver to concentrate on the road
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## Other cards in this set

### Card 2

#### Front

What are the units for momentum?

kgm/s

### Card 3

#### Front

What is the formula for force?

### Card 4

#### Front

How can the force be reduced?

### Card 5

#### Front

How can force be educed by reducing the acceleration?