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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
incline. 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 63 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 5
g block and the 10 g 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 10 g block up the incline (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 incline 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 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 incline planes include stairs and slides.
Experiment with the inclined plane by changing its height (figure
2D). Does a higher incline increase or decrease the amount of
effort needed? At the same time, drop a ball beside the incline
from the same height and roll a second ball down the incline.
Which ball reaches the bottom first? Less force is needed to
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accelerate the ball down the incline; 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 incline 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.
In a third-class lever, the fulcrum point is also located on one
end, but this time the applied effort is in the center between
the fulcrum point and load. An example of this type of lever is a
fishing pole. When fishing, the arm acts as the fulcrum point, the
effort is applied to the center of the rod, and the load is at the
end of the fishing line. The load moves in the same direction as
applied effort. Set up the model with the rod resting on one end
of the fulcrum and place one wheel on the other end. Lift up the
center of the rod to demonstrate a third-class lever (figure 4D).
Notice how the load is raised in the same direction as the effort.
Wheel and Axle (figure 5)
A wheel and axle is one of the most common and useful simple
machines. Its purpose is to move objects from one place to
another with very little effort. Movement is accomplished
by rolling an object while the wheel is turning on the axle.
Demonstrate this principle by creating the doorknob model
(figure 5C). Roll the wheel back and forth and watch the axle
turn.
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