Multilinguismo, CLIL e innovazione didattica - Libera Università di ...

Responsibilities and competences of the CLIL teacher
Appendix 1
THE UNIT ON LEVERS
INTRODUCTORY PHASE
SIMPLE MACHINE
A simple machine is a mechanical device that changes the direction or magnitude
of a force.
In general, they can be defined as the simplest mechanisms that use mechanical
advantage (also called leverage) to multiply force.
A simple machine uses a single applied force to do work against a single load
force. Ignoring friction losses, the work done on the load is equal to the work
done by the applied force. They can be used to increase the amount of the
output force, at the cost of a proportional decrease in the distance moved by
the load. The ratio of the output to the input force is called the mechanical
advantage. Usually the term refers to the six classical simple machines which
were defined by Renaissance scientists:
▪ Lever
▪ Wheel and axle
▪ Pulley
▪ Inclined plane
▪ Wedge
▪ Screw
Simple machines do not contain a source of energy, so they cannot do more
work than they receive from the input force. When friction and elasticity are
ignored, the work output (that is done on the load) is equal to the work input
(from the applied force). The work is defined as the force multiplied by the
distance it moves.
They are the elementary "building blocks" of which all more complicated
machines (sometimes called "compound machines" to emphasize that they are
combinations of the simpler building blocks) are composed. For example,
wheels, levers, and pulleys are all used in the mechanism of a bicycle.
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