friction and breaking distance - wordpress.com · 2015-12-10 · friction and breaking distance...

Friction and

Breaking

Distance Book pg 16 -18, 26 - 27

Syllabus 1.14, 1.19

10/12/2015

©cgrahamphysics.com 2015

Reflect

What is the relationship between mass,

force and acceleration?

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Aim

What is friction?

Apply Newton’s 2nd Law

Find one photo not posted here

that has to do with friction

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What is friction?

What is friction and why is it an important force?

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Friction is a resistive force that slows things down and tries

to stop objects sliding past each other.

What is friction?

What would happen if friction didn’t exist?

friction pulling force

Friction always acts in the opposite direction to which an object is moving

or trying to move.

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Friction – useful or a problem?

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What causes friction?

Friction occurs between two objects because the surfaces of

those objects are rough, and contain bumps and hollows.

This roughness

means that a force

is needed to move

the two objects over

each other.

Even objects that appear very smooth, such as polished metal

or ice, have a rough surface if viewed under a microscope.

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Different types of friction Friction is most obvious when it acts between two solid

objects, but it also acts between solid objects and gases,

and between solid objects

and liquids.

Friction caused by an

object moving through air

is called air resistance. Friction caused by an

object moving through a

liquid, such as water, is

called drag.

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How does friction change?

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Friction always tries to stop things moving or slow

things down. What effect does this have?

Reducing the effects of friction

Friction creates heat and eventually wears down surfaces,

which can be very damaging.

Lubricants are used to

reduce friction in machinery

and so help protect surfaces.

In car engines, oil is used

as a lubricant.

Bearings and rollers can also be used to reduce friction,

for example, in wheels

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Stopping a car…

What two things must the driver of the car do in order to stop in time?


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What causes car crashes?

Write down everything you can think of

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Break it down:

Human factors

Car or road factors

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Thinking distance

What effects the thinking

distance?

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alcohol

other drugs and

some medicines

tiredness distractions,

such as

mobile phones speed

What affects thinking distance?

What factors affect thinking distance?

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Brakes have been applied

Braking distance

What effects the

braking distance?

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weather

condition of

tyres/brakes

What affects braking distance?

The braking distance is the distance a vehicle takes to stop

once the driver has applied the brakes.

What factors affect braking distance?

condition of road

speed

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Thinking distance Braking distance

Stopping distance

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Stopping a car…

Braking distance

Too much alcohol

Thinking distance

Tiredness

Too many drugs

Wet roads

Driving too fast

Tyres/brakes worn out

Icy roads

Poor visibility

+

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Experiment Get your partner

to drop the ruler

vertically.

React and catch

it!

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Reaction times.

What is your reaction time?

Reaction time

10cm

20cm

30cm

40cm

50cm

0.14s

0.20s

0.24s

0.28s

0.31s

Task: Measure it three times and

take an average.

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Reaction time ___ secends

Speed

(mph)

Speed

(m/s)

Thinking distance

(speed x reaction time)

20 8.9

30 13.4

40 17.8

50 22.3

60 26.8

70 31.2

80 35.7

100 44.7

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Representing Stopping Distance Graphically

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Typical Stopping distances YouTube - Top Gear 13-5: RWD Braking Challenge

YouTube - Think! - Slow Down (Extended) (UK)

10/12/2015 ©cgrahamphysics.com 2015

http://www.youtube.com/watch?v=Bij6YTnxlqc






http://www.youtube.com/watch?v=ipnJbSnmc24







friction and breaking distance - wordpress.com · 2015-12-10 · friction and breaking distance...

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