Learning Resources LER 2442 Manual page 8

Simple machines, an important part of everyday life, simplify
work tasks such as lifting, pulling, and pushing objects.
Simple machines allow a person to exert less energy and
effort to accomplish a task. For example, lifting a heavy box
into a truck requires much more force and effort than pushing
the box up an inclined. Simple machines can also reduce
the amount of force needed to move an object or change the
direction or distance of force required.
This kit includes sixty-three components to build five basic
simple machines: pulley, inclined plane, wedge, lever, and
wheel and axle. Each machine is designed to decrease force
and effort in its own way.
Pulley (figure 1)
A pulley's main function is to change the direction of an
applied force, which, in turn, decreases the amount of effort
and force needed to move an object. Applying a downward
force on a pulley will move an object upward. Demonstrate this
principle by looping the string and hook of the 10g block over
one pulley wheel and pull downward on the hook (figure 1F).
Notice how the block moves upward while the hook is being
pulled downward. The applied force changes the direction in
which the block moves, making it easier to move upward.
Imagine a construction worker trying to push a large beam
to the top of a building. It would be easier to lift the beam
upward using a machine with a pulley system.
A pulley consists of a cord or wire moving over at least one
wheel or a system of wheels. Real-life examples of pulleys
include a flag pole, construction crane, window blinds, and
older elevators.
Experiment with the pulley model by changing the location,
amount, or size of the wheels (figure 1G). Add washers to
the end of the hook. How many washers does it take to move
the 5g block and the 10g block? Does effort change when
moving the string through more or less wheels? How does the
direction change? Does effort increase or decrease when using
small or large wheels? Does effort change when the location of
the wheels changes? How does the direction change?
Inclined Plane (figure 2)
An inclined plane's main purpose is to move an object to a
certain height by pulling or pushing it with less effort and
force over a greater distance. Demonstrate this principle by
pulling the 10g block up the inclined (figure 2B). Then, set
the block down on the table and lift it straight up to the same
height. Notice how it is easier to pull the block up the inclined
than manually lifting it upward. Pulling the block requires a
greater distance, but the inclined plane eases the process.
Imagine a person loading boxes by lifting them from the
ground and placing them in the back of a truck. It would be
easier to carry or push boxes up a ramp. Even though the
7
distance is greater, an inclined plane exerts less effort than
manual lifting.
An inclined plane consists of a ramp leading to another level.
Real-life examples of inclined planes include stairs and slides.
Experiment with the inclined plane by changing its height
(figure 2D). Does a higher inclined increase or decrease the
amount of effort needed? At the same time, drop a ball beside
the inclined from the same height and roll a second ball down
the inclined. Which ball reaches the bottom first? Less force
is needed to accelerate the ball down the inclined; therefore,
that ball should reach the bottom last.
Wedge (figure 3)
The purpose of a wedge is to split or separate objects into
two or more pieces by inserting a sharp-edged inclined into
another object. Demonstrate this principle by inserting the
wedge piece between two bases linked together by rubber
bands (figure 3B). Notice how the space between the two
bases increases as the wedge is inserted.
Imagine the front of a boat moving through water. The pointed
tip, or wedge, makes the boat move more easily. The boat
would not move as efficiently through water if its front was
merely a flat surface.
A wedge consists of at least one, but usually two, inclined
planes put together. Some real-life examples of wedges
include knives, axes, chisels, and boat fronts.
Lever (figure 4)
There are three different types of levers, but each one has
a few things in common. All levers have a bar, rod, or other
surface that rests on a fulcrum point. Force is applied to one
end of a rod, which, in turn, moves a load. If a load is located
close to the fulcrum point, less effort is required.
In a first-class lever, the fulcrum point is located in the middle
of the load. A seesaw is an example of a first-class lever, which
applies the force in one direction with the load moving in the
opposite direction. Set up the model with the rod resting on
the center of the fulcrum and place two wheels on either end
of the rod to demonstrate this principle (figure 4B). Notice
when one end is pushed down, the other end rises.
In a second-class lever, the fulcrum point is located on one
end, with the load located between the fulcrum point and
applied effort. A wheelbarrow is an example of a second-class
lever. The load is in the center and the fulcrum point is the
wheel. Effort is applied to the handles, allowing a person to
lift and easily move the load. Set up the model with the rod
resting on one end of the fulcrum and place one wheel in the
center. Lift up the other end of the rod to demonstrate this
principle (figure 4C). Notice how the load is raised in the same
direction as the effort.