BACKGROUND:
A machine captures motion and is
capable of transforming motion into useable energy. Modern machines are
very complex; but are essentially a combination of one or more of three
basic elements: the wheel and axle, the lever, and the inclined
plane.
A wheel and axle is a wheel that turns on a post, or axle. It's
used to move or roll things. A lever is a rigid body that moves at
a point called fulcrum. An inclined plane reduces the force needed
to move an object by increasing the distance through which the force
must move.
Some simple machines are combinations of these basic
elements. A screw and wedge is a modified
inclined plane. In the screw, the inclined plane is wrapped around a
cylinder in a spiral pattern. It moves by twisting , usually with
a screw driver. It's not an efficient machine because you waste a
lot of force due to friction. A wedge is made of two inclined
planes meeting at a point. A wedge can be used to cut something or
hold something in place. An inclined plane does not move while a
wedge does. A pulley is a chain, rope, or belt wrapped around a wheel. A
pulley can be fixed or movable. A gear which is not considered a
simple machine is a wheel
and axle with levers around.
The general function of machines is
to generate power and to transmit that power through work. Machines,
whether simple or complex, make life easier for humans. Make sure
students know that machines are made almost exclusively by humans. Some
monkeys and gorillas fashion primitive tools.
PROCEDURE:
- The enclosed sheets will help you
to review simple machines. Make sure to explain that simple machines
help make work easier; and that most machines we see today are complex
machines, made up of a series of simple machines that work in harmony.
- Inclined plane uses the principle
that if you extend the distance to perform a task it will become easier.
The saw and a shovel are designed to slowly use force (usually from a
human) to make work easier.
- The lever uses a similar principle
except it concentrates power in a certain area, which makes the task
easer to perform.
- A wheel and axle transforms
energy efficiently and quickly.
- Have the students cut out the six examples of
simple machines. Paste 3 cut-outs on the left hand side of
each side of the construction paper
- Ask students to cut out the 12 machines and
try to sort them based on the simple machines found. In some
cases, there are more than one type of simple machines found.
Answers:
inclined plane: A1, B2 ; wheel and axle: A2, C1; screw: D2, D3
lever: B1, C3 (A1 and C1 have levers, too); pulley: A3, D1; wedge:
B3, C2
