Download Mechanisms - DOWNEND SCHOOL

Mechanisms
These icons indicate that detailed teacher’s notes or useful web addresses are available in the
Notes Page.
This icon indicates the slide contains activities created in Flash. These activities are not editable.
For more detailed instructions, see the Getting Started presentation.
1 of 15
© Boardworks Ltd 2004
Making our lives easier
2
The aim of technology is to improve life for people.
Machines and mechanisms make it easier for us to move
things.
Mechanisms and machines are all around us.
Look around the room that you are in at the
moment.
Identify an everyday machine or mechanism.
How does this machine or mechanism make life
easier?
2 of 15
© Boardworks Ltd 2004
The first machines
3 of 15
© Boardworks Ltd 2004
Early ‘wheels’
4 of 15
© Boardworks Ltd 2004
From rollers to wheels
No one knows for sure how the wheel was ‘invented’.
Perhaps the idea ‘developed’ in stages.
Trees cut down to make
log rollers.
Logs cut into short
pieces – solid wheels.
Solid wheels lightened
by cutting out bits –
spokes.
Rubber tyres used to
improve efficiency.
5 of 15
© Boardworks Ltd 2004
Military machines
6 of 15
© Boardworks Ltd 2004
Animal power
From early times people have used animals to make life
easier for themselves.
Horse power was used to help lift loads.
Can you think of any other examples of animal
powered machines?
7 of 15
© Boardworks Ltd 2004
Levers in action
Levers are very simple machines.
If you look you will see examples of levers all around.
How many other examples of levers can you think of?
8 of 15
© Boardworks Ltd 2004
Levers
9 of 15
© Boardworks Ltd 2004
Mechanical advantage
Levers can be used to increase our strength.
With a long lever, a small force can be used to raise a
large load.
This gives a mechanical advantage.
Mechanical advantage (MA) = load
effort
Load = 50 N
Effort = 10 N
MA = 5
Effort =
10 newtons
Load =
50 newtons
10 of 15
© Boardworks Ltd 2004
Velocity ratio
Velocity ratio is used to compare the distances moved
by load and effort.
Here, in one second, the
effort moves 1 metre and
the load moves 4 metres.
Because the applied force
is greater than the load,
the load moves faster
(and further) than the
effort.
Velocity ratio =
distance moved by effort
distance moved by load
11 of 15
© Boardworks Ltd 2004
Torque
The force that is used to
undo a nut and bolt is a
turning force.
This turning force is called
torque.
The longer the handle on
the spanner the easier it
will be to undo the nut
because the torque will be
greater.
Torque = force x distance.
12 of 15
© Boardworks Ltd 2004
Types of motion
13 of 15
© Boardworks Ltd 2004
Types of gears
Gears used to change rotational
motion through 90 degrees:
bevel gears
worm and wheel
Gears used to change rotation
into linear motion:
rack and pinion
14 of 15
© Boardworks Ltd 2004
Inside the black box
15 of 15
© Boardworks Ltd 2004