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Technology: Engineering Our World
Machines help us to produce food on the land and make the electronics
you play with. They help us dig trenches and bore tunnels. Around the
home, the automatic washing machine, lawn mower, and vacuum cleaner
lighten our workload. The dentist’s drill removes decay from our teeth.
The jet plane speeds us to our vacation site.
A machine is a device that uses energy to do some kind of work. For
example, a lawn mower uses gasoline to trim the lawn. Machines do
not need to be large or complicated. A knife, a bottle opener, and a claw
hammer are also machines.
Machines have been used for thousands of years to make work easier.
For example, people discovered that they could lift heavy objects more
easily by throwing a rope over a tree branch. This allowed them to pull
down instead of lifting to move the objects. This idea was later refined to
use a wheel with a groove for a rope, chain, or belt. See Figure 8-1.
Simple Machines
Over the years, six basic types of machines were developed. They
include the lever, pulley, wheel and axle, inclined plane, wedge, and
screw. We refer to these as simple machines. These six simple machines can
be divided into two groups. One is based on the lever, and the other is
based on the inclined plane. See Figure 8-2.
gure 8-1. Changing the direction of
applied force makes it easier to lift heavy
objects. As the woman pulls down on the
rope, the pail moves upward.
Inclined plane group
Screw
Wedge
Inclined plane
Lever group
Pulley
Lever
Wheel and axle
Wheel
Axle
gure 8-2.
continue to be important inventions.