11. MACHINES
11.1 Before you read the text answer the question:
What simple machines let people apply less force to perform work?
11.2 Read and translate the text.
MACHINES
Machine, simple device that affects the force, or effort, needed to do a
certain amount of work. Machines can make a tough job seem easier by enabling
a person to apply less force or to apply force in a direction that is easier to
manipulate. Machines lessen the force needed to perform work by lengthening
the distance over which the force is applied. Although less force is subsequently
used, the amount of work that results remains the same. Machines can also
increase the speed at which work makes an object travel, but increasing speed
requires the application of more effort.
The history of machines dates back thousands of years. Although the date
of the first use of simple machines is not known, the lever is believed to be the
first simple machine that was utilized by humans. The first levers were probably
branches or logs used to lift heavy objects. People used a counterbalanced lever
called a shadoof in ancient Egypt for lifting irrigation water. Metal or stone
wedges have been used since ancient times for splitting wood. The Greek
inventor Archimedes (287-212 BC) developed a screw-type device known as
Archimedes’ screw for raising water. Some modern water pumps still use this
principle. According to legend, Archimedes also used a block and tackle to pull
ships onto dry land.
There are four types of simple machines: the lever, the pulley, the inclined
plane, and the wheel and axle. Each machine affects the direction or the amount
of effort needed to do work. Most mechanical machines, such as automobiles or
power tools, are complex machines composed of many parts. However, no matter
how complicated a machine is, it is composed of some combination of the four
simple machines. Although these simple machines have been known and used for
thousands of years, no other simple machines have been discovered. Two other
common simple machines, the screw and the wedge, are really adaptations of the
inclined plane. Some common examples of simple machines are the shovel (a
form of lever), the pulley at the top of a flagpole, the steering wheel of an
automobile (a form of wheel and axle), and the wheelchair ramp (a form of
inclined plane).
11.3 Match these words with the appropriate explanation
1. amount
a. difficult
and
requiring
determination or effort
2. tough
3. lever
4. shadoof
5. wedge
6. split
7. tackle
8. pulley
9. inclined plane
10. mechanical
b. break or cause to break forcibly
into parts, especially into halves
c. a device consisting of a wheel
over which a rope or chain is
pulled in order to lift heavy
objects.
d. a
quantity
of
something,
especially the total of a thing or
things in number, size, value, or
extent
e. a mechanism consisting of ropes,
pulley blocks, hooks, or other
things for lifting heavy objects
f. a plane inclined at an angle to the
horizontal
g. a handle or bar that is attached to
a piece of machinery and which
you push or pull in order to
operate the machinery.
h. a pole with a bucket and
counterweight used esp. in Egypt
for raising water
i. operated by a machine or
machinery
j. a piece of wood, metal, or some
other material having one thick
end and tapering to a thin edge,
that is driven between two objects
or parts of an object to secure or
separate them
11.4 Mark the sentences with T if they are true and with F if they are false
1. Machine, simple device that are affected by the force, or effort, needed to
do a certain amount of work.
2. Machines lessen the force needed to perform work by lengthening the
distance over which the force is applied.
3. The date of the first use of simple machines is mentioned in Archimedes’
works.
4. Metal or stone wedges have been used since ancient times for splitting
wood.
5. No matter how complicated a machine is, it is composed of some
combination of the four simple machines.
11.5 The word affect in paragraph 1 is closest in meaning to
1. influence
2. disturb
3. interrupt
4. say
5. distinguish
11.6 The word believed in paragraph 1 is closest in meaning to
1. concerned
2. influenced
3. hoped
4. written
5. supposed
11.7 The word composed in paragraph 1 is closest in meaning to
1. written
2. done
3. put
4. consisted
5. divided
11.8 Match the things with simple machines 1-4 which form these things have
the pulley at the top of a flagpole
the shovel
the wheelchair ramp
the steering wheel of an automobile
1. lever
2. pulley
3. wheel and axle
4. inclined plane