BACKGROUND:
Although gears, wheels, pulleys, and
other machines are simple in design, they were needed before humans
could reason into higher levels of technology. The mechanics and physics
of these simple devices were not realized when they were discovered, the
machines just worked. In order to fulfill basic everyday needs, early
humans sought ways to satisfy them. Thus using bone, wood, and stone
they fashioned simple tools for digging, killing, and scraping. When
early humans wanted to move items or get items they wanted, they would
use reason to "invent' these devices.
The principles of simple machines
have been used throughout the centuries from moving large blocks to
build the Pyramids in Egypt to using tractors today. Young students
sometimes are not aware of simple machines, even though they use them
every day. Educators must make students aware of how simple machines are
used in our lives.
PROCEDURE:
- The following are questions to
start class discussions on simple machines.
What are simple machines?
(Something that people have created to do work. The simplest machines
range from crowbars to eggbeaters).
Could we live without machines?
(No. Something as simple as a cart requires wheels to move. Ask students
how their clothes are cleaned, what do we use to cook food, and how do
they get to school on rainy days. They should conclude that it would be
very hard to live without machines).
- Have students look around the
classroom and identify simple machines. Make sure to include pencil
sharpeners, carts, push pins, scissors and any other machine.
- Discuss with students that simple
machines are all around us. Make sure the students understand how simple
machines have been used in everyday life, from cavemen to modern humans.
- As a follow-up activity, students
can find examples of simple machines in the classroom and in their
homes. Some types of machines may be difficult to break down into one of
the six types and this may lead to a good class discussion. Even if no
"right" answer emerges, the students will realize that
machines are all around them. Many simple looking items are going to be
combinations of the basic types. Possible examples:
- Pulleys: Venetian blinds, cranes
- Levers: see-saws, electric switches, crowbars, oars, jacks,
wheelbarrows, shovels, scissors, pliers, and nutcrackers (all are
pairs of levers)
- Inclined planes: stairs, ramps and mountain roads
- Wedges: axe blades, chisels, wood splinters, blades of knives,
scissors, nails, pins and needles
- Wheels and axles: doorknobs, anything with a crank and wheel
- Screws: vise, screws and jack screws
- Gears: egg beaters, clocks
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