There are many
different types of machines with varying capabilities
and functions. This section is about common simple
machines which are everywhere around us.
inclined plane is a simple machine with no moving
parts. It is simply a
straight slanted surface set at an angle
(other than a right angle) against a horizontal surface
used to raise an object. Examples of inclined planes
include ramp, slanted road, slide, and path up a hill.
following figure shows an inclined plane. The length A
is the base, length B is the height, and length C is the
inclined plane. With the use of the inclined plane a
given resistance can be overcome with a smaller force
than if the plane is not used. For example, in the
figure, suppose we wish to raise a weight of 100 kg
through the vertical distance B = 2 m. If this weight
were raised vertically and without the use of the
inclined plane the force 100 kg would have to be exerted
through the distance B. However, if the inclined plane
is used and the weight is moved over the inclined plane
C, a force of only 2/3 of 100 kg or 66.7 kg is required.
Remember, this force is exerted through a distance C
which is greater than distance
Using an inclined
plane requires a smaller force exerted through a greater
distance to do a certain amount of work. Letting F
represent the force required to raise a given weight on
the inclined plane, and W the weight to be
raised, we have the proportion:
In our daily life,
lifting an object straight up is heavier than pulling it
up an incline plane, we do not need to use as much
force. However, the inclined plane is longer. Inclined
planes can also be used in reverse to slow things down
to a stop. It is easy to find applications of inclined
planes everywhere: Ramps for wheelchairs, steps, a ski
jump, car ramps, playground slide, boat ramps, etc.
See this simulation
gear, the wheel and axle, and the pulley are all kinds
of wheels, with small alterations. A gear is a
wheel with accurately machined teeth round its edge. Its
purpose is to transmit rotary motion and force. Basic
relationships for a gear are the number of teeth, the
diameter, and the rotary velocity of gears. Gears being
an important part of a machine have many applications
within various industries. These industries include
automotive industries, steel plants industry, paper
industry, in mining and many more. They are used as
conveyors, elevators, separators, cranes and lubrication
The following figure shows the ends of
two shafts A and B connected by 2 gears of 12 and 24
teeth respectively. The larger gear will
make only one-half turn while the smaller makes a
complete turn. That is, the ratio of speeds (velocity
ratio) of the large to the smaller is as 1 to 2. The
gear that is closer to the source of power is called the
driver, and the gear that receives power from the
driver is called the driven gear. The ratio
between the rotation speed of the driven gear and the
rotation speed of the driver is called the gear ratio.
basic mechanism is the lever, a bar which rests, or
pivots, on a fulcrum.
A seesaw is a
familiar example of a lever in
which one weight balances the other.
The hammer is another example of lever
when it is used to pull a nail out of a piece of wood.
have at least two basic purposes. One is to lift or move
a load at one place on the lever by making an effort at
another location of the bar. The second is to apply a
force to an object by exerting the force elsewhere.
Levers can be used to change the distance and power of
All levers have three basic parts:
the fulcrum, a force or effort, and a
There are three types of levers
as shown in the figure.
The location of the fulcrum in
the resistance (or weight) and the effort determine the
Common examples of first-class levers
include crowbars, scissors, pliers, tin snips and
playground seesaws. Examples of second-class levers
include nut crackers, wheel barrows, and certain types
of bottle openers. The human bicep muscle is an example
of a third class lever.
A screw is a shaft with a thread or
groove wrapped around it to form a helix. While turning,
a screw converts a rotary motion into a forward or
backward motion. By rotating the screw (applying a
torque), the force is applied perpendicular to the
groove, therefore translating a rotational force into a
linear one. It is frequently used to fasten objects
The wedge allows motion from objects such
as hammers to be transferred into a breaking, cutting,
or splitting motion. The force is perpendicular to the
inclined surfaces, so it pushes two objects (or portions
of a single object) apart. A wedge converts motion in
one direction into a splitting motion that acts at right
angles to the blade. Nearly all cutting machines use the
wedge including knifes. A lifting machine may use a
wedge to get under a load.
and pulleys are an important part of most
machines. Pulleys are gears without teeth and instead of
running together directly they are made to drive one
another by cords, ropes, cables, or belting of some
kinds. As with gears, the velocities of pulleys are
inversely proportional to their diameters.
Examples of where pulleys can be
used include flag poles, sailboats, blinds, and cranes.
The following figure shows belt and pulleys. Pulleys can
also be arranged as a block and tackle.
are common today in the form of various tools . The same
physical principles and mechanical application of simple
machines used by ancient engineers to build pyramids are
employed by modern engineers to construct various
structures such as houses, roads, bridges, and