# 1.2.4 CAR SAFETY

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What is thinking distance?
The distance travelled by the car from when the driver sees the problem and the brakes are applied (reaction time)
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How do you calculate thinking distance?
vehicle speed x reaction time
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What is breaking distance?
distance travelled by a vehicle from the moment when the breaks are applied until the vehicle comes to a stop
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What is stopping distance?
sum of thinking and breaking distances
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Describe the factors that affect thinking distance
alcohol levels // tiredness // distractions // age - reaction time decreases with age
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Describe the factors that affect breaking distance
road surface (wet, icy, oily) // quality of breaks // quality of tyres (all these factors decrease amount of friction)
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Describe the factors that overall impact upon the stopping distance
speed, mass, gradient of road (uphill means shorter distance) // greater speed means greater distance // greater mass means greater distance
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What do air bags and seat belts do?
Reference to K.E.=Fs or 1⁄2 mv2=Fs // prevents collisions with steering wheel/ windscreen/dashboard // time / distance for stopping is more // smaller deceleration
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What is a crumple zone?
part of a car which has been specifically designed to squash up or crumple easily in the event of a crash // absorbs energy // directs engine away from passengers
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What happens when a car decelerates quickly?
objects within the car obey Newton's 1st law // continue to move forwards at car's impact velocity until a force changes their motion
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How do air bags work?
tiny accelerometer detects large deceleration // accelerometer consists of two rows interlocking teeth // on deceleration teeth collide generating a voltage // magnetic sensor triggers electrical signal to release bag
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How do GPS work?
several satellites used / satellite in high orbit transmit radio / micro waves // transmission contains identity, transmission time, position //delay time is determined and is used to calc distance between - multiple transmissions (trilateration)
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What are GPS used for?
navigation for boats/ cars/ planes // vehicle tracking // mobile phones locations
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Describe car safety in terms of F=ma
change in v = acceleration // big a = small t = big F // big t = small a = small F // increase in impact time decreases resultant force
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Describe car safety in terms of W=Fx
on impact energy is transferred // KE goes into sound or thermal // work is done transferring this energy // work done = KE lost // maximise x will minimise F
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## Other cards in this set

### Card 2

#### Front

How do you calculate thinking distance?

#### Back

vehicle speed x reaction time

### Card 3

#### Front

What is breaking distance?

### Card 4

#### Front

What is stopping distance?

### Card 5

#### Front

Describe the factors that affect thinking distance