BACKGROUND:
Simple machines are a part of the
physics discipline of "mechanics." Simple machines change the
direction of an applied force, change the strength of a force necessary
to do a job, or does both. Simple machines can also be used to apply a
force to a place that cannot otherwise be reached or applies force in
ways that cannot be done without machines.
The definition for "tool"
overlaps that of "machine". According to Webster's dictionary,
a tool is something held in the hand and used for cutting, hitting or
digging, with things such as knives, saws, hammers or shovels. Tools can
also be the working part of a power machine, for example, a drill bit.
In other words, an item that is called a machine based on what it does,
can be described as a tool based on how it is used. Students will be
studying kitchen tools.
There are three basic elements of
simple machines including wheel and axle, lever, and
inclined plane. All simple machines that will be discussed are a
combination of these basic elements.
PROCEDURE:
-
Explain the principle of a
lever.
A lever is basically a simple machine consisting of a rigid body
pivoted on a fixed fulcrum. Before beginning this exercise, it is
necessary to explain the terms "rigid body" and
"fulcrum". The most familiar lever is the see-saw. The rigid
body is where the student sits, and the fulcrum is the base that
supports the rigid body.
- Using a board and a fulcrum (half log), see if
the students can figure out how to lift you. Don't give them
too many clues. Try moving the fulcrum to different positions
or having students of different weights.
- A scissor illustrates a
lever. The point at which the scissor opens and closes is the fulcrum.
Ask students to cut the letter L from a piece of paper. Write lever
on the L.
- Put some peanuts (Make sure no one is allergic to
peanuts or nuts in general!) in a tray, ask students to crack the
peanuts with a nut cracker.
- Peel an apple to show the students
how the peeler moves like a lever.
- Put a boiled egg or a ball of
playdough on the egg slicer, then slice the object by pulling down
the top.
-
Point out that levers help make it easier to lift, move, or break heavy
or large objects.
-
Discuss screws. This is one case where the force being applied
travels very far to make the insertion of a screw easier. Everyone knows
what screws are but most children think that shop screws are the only
kind.
- A cork screw and fruit twister illustrate a screw. If you have
oranges, students can "screw" the fruit twister for some
juice. You can also use playdough instead of oranges. Ask
students to twist the twister into the playdough.
Wheel and axles work by using the motion of a wheel to move
objects with less friction.
- A rolling pin and pizza cutter can be used to illustrate wheel and
axle. Students can roll out playdough to a thin sheet.
Then cut it with the pizza cutter.
- Corn skewers can illustrate wheel and
axle. To illustrate the corn skewers, put them in an apple (or other
fruit) so students can see how you can easily turn the fruit.
Talk about how gears are
used to change the speed of turning and to go around corners.
-
An ice cream scooper, can opener and eggbeater illustrate gears.
Point out the gears and let the students turn the tools. You may want
students to actually scoop some ice cream! Eggbeaters can be used to
make bubbles in a tub of bubble solution.
