Archimedes' screw is an inclined plane wrapped around a wedge
placed inside a tube. It has been used since ancient times to lift
water. The device, often used to direct water into an irrigation
channel, was composed of a wooden beam, several feet long, around
which a spiral screw thread was built of layers of flexible,
pitch-covered wood strips.
Over this thread were
fastened tight-fitting narrow planks running the length of the beam
and giving it the appearance of a tube.
To operate the screw, it is angled into the water so that some
part of the inclined plane is in the water. When the handle of the
screw is turned the right way, the water is lifted up until it
flows out of the tube's upper end.
Six simple devices
Levers are simple
devices that make our work easier. There are at least three parts
in a lever. They are the fulcrum, the resistance, and the force.
There are three kinds of levers.
First Class Lever
In a first class lever, the fulcrum is in the middle; the
resistance is at one end and the force is at the other end.
Examples of the first class lever are scissors, crowbars, and
Second Class Lever
A second class
lever has the force on one end, the fulcrum on the other and the
resistance in the middle. Examples of this lever are nutcrackers,
oars of a boat, and wheelbarrows.
Third Class Lever
In the third class lever, the
resistance is at one end, the force is at the middle, and the
fulcrum is at the other end. Tweezers, baseball bats, and your arm
are all examples of third class levers.
Pulleys are made of a
spool and a rope. They are used to move elevators, raise flags, and
many other things.
Wheel and Axle
A wheel and axle helps make lifting things easier. It works by
turning the wheel.
It helps to make
lifting things easier.
A wedge helps keep things
A screw is an inclined plane wrapped around a wedge. See