Mechanisms

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Mechanisms

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2Making our lives easier

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?


The first machines


Early ‘wheels’


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.


Military machines


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?


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?


Levers


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.

Load = 50 newtons

Effort = 10 newtons

Load = 50 NEffort = 10 NMA = 5

Mechanical advantage (MA) = loadeffort


Velocity ratio

Velocity ratio is used to compare the distances moved by load and effort.

Velocity ratio =

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.

distance moved by effort

distance moved by load


Torque

Torque = force x distance.

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.


Types of motion


Types of gears

Gears used to change rotation into linear motion:

Gears used to change rotational motion through 90 degrees: bevel gears

rack and pinion

worm and wheel


Inside the black box

Mechanisms

Business

Transcript of Mechanisms