Transcript Stopping distances for cars

Stopping distances for cars
Know your speed limits – fill in the missing speeds
?
Built up area
Built up area
Single carriageway
Dual carriageway
Dual
carriageway is
ending
Motorway
Know your speed limits – fill in the missing speeds
?
Lesson objective: know your
stopping distances
Lesson outcomes:
E•
C•
A•
State what is the meaning of braking distance,
thinking distance and stopping distance.
Describe what can affect the braking distance,
thinking distance and stopping distance.
Explain – aquaplaning
Would you like a car?
Visit nice places
Well, you need to pass your test
first!
A written exam and a practical
exam
Stopping distances
How long does it take a moving vehicle to stop?

The
Thinking
Braking
stopping
distance
distance
is the
distance
is the
distance
distance
is the a
sum
a
carcar
of
the
travels
travels
thinking
before
whilst
thethe
distance
brakes
brakes
and
areare
the
applied.
braking
being distance.
applied.

Braking
distance
Thinking
distance
Stopping distance
Stopping distance = thinking distance + braking distance
Thinking distance
The distance the car travels in the split
second between a hazard appearing and
the driver applying the brakes
Braking distance
The distance the car travels during its
deceleration, whilst the brakes are
being applied
The total stopping distance =
thinking distance + breaking
distance
30mph
9m +
14m = 6 car lengths
50mph
15m +
21m +
38m = 13 car lengths
75m = 24 car lengths
70mph
Thinking distance
It is affected by 3 main things:
1. How fast you are going
2. Being wide awake – drugs, tiredness,
alcohol, carelessness and old age.
3. Visibility – rain, oncoming lights, fog
and the night.
Braking distance
It is affected by 4 main factors:
1. How fast you are going
2. The mass (or load) of the vehicle
3. If the car is poorly maintained – brakes
and tyres (groves in tyres – 1.6mm deep)
4. The grip of the road surface – on a wet
road you can skid twice as long
Why is this illegal?
How will this affect your stopping
distance?
A bald tyre
has more
contact on
the road and
therefore
more
friction!
Bald tyres
make
stopping
distances
shorter on
dry roads,
Why
What about aquaplaning ?
• On a wet road, tyre treads channel water
out from between the tyre and the road
Removing
the water
away from
the tyre and
the road
What about aquaplaning ?
• Bald tyres allow a thin layer of water to
stay between the tyre and the road,
reducing friction
Why do racing
drivers change
their tyres when it
is wet?
Can you match up the words with their
definitions?
Stopping distance
One of forces the road exerts on
the tyres as the car is stopping.
Friction
The distance a car travels whilst
it is braking.
Thinking distance
The distance a car travels before
the brakes are applied.
Braking distance
The sum of thinking distance
and the braking distance.
What factors affect braking and thinking distance?
Thinking distance
Braking distance
Speed of car
Speed of car
Drugs and alcohol
Road conditions
Tiredness
Condition of tyres
Medication
Condition of brakes
Medication
Speed of car
Condition of tyres
Drugs and alcohol
Road conditions
Tiredness
Condition of brakes
Braking car question:
A car is moving along an open road. Suddenly, a sheep walks into the
road.
a) What do we call the distance the car travels before the driver puts their
foot on the brakes?
Thinking distance
b) Name one factor that could increase the distance the car travels in this
time.
Medication, drugs/alcohol, speed of car, tiredness
c) The braking distance is 35m for the car. If the stopping distance is
50m, how far did the car travel before the driver put their foot on the
brakes?
Thinking distance
= Stopping distance – braking distance
= 50m – 35m
= 15m
http://www.driving-test-success.com/theory/stopping-speed/stopping+speed.htm
Stopping a car…
Tiredness
Too many
drugs
Thinking
distance
Poor
visibility
Wet roads
Icy roads
Tyres/brakes
worn out
Too much
alcohol
Braking
distance
Driving too
fast
Speed kills
What other measures are
taken to stop motorists from
speeding?
Thinking distance
The distance the car travels in the split
second between a hazard appearing and
the driver applying the brakes
Reaction timer
You can test your reactions by holding the top of a 30cm
ruler, hanging vertically between a partners finger and
thumb.
When you let go (no warning) your partner has to grip the
ruler as quickly as possible.
The slower your partner's reaction time the further the ruler
will fall( see table, page 138, physics for you).