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Why it works
Levers are
simple machines
,
with only two parts, that are
used to increase force. The
“arm” of the lever is the part
that you push or pull. The
point around which the lever
turns is called the fulcrum.
Some levers help to lift heavy
loads—the load is the object
you are trying to lift. The
effort is the force you use
to push down on the lever
to lift the load. Ben is right:
when using a lever, the closer
the fulcrum is to the load,
the less effort is needed to
lift the load.
Experiment with moving a lever’s
fulcrum to see how it affects the
effort needed to lift a load.
You need:
l
a footlong ruler (30 cm)
l
pencil
l
tape
l
two paper cups
l
pebble, or other weight
l
coins (all the same type)
Prove it!
Label one cup “Load” and the other
“Effort.” Stick the cups to opposite
ends of the ruler. Put the pencil
under the ruler, below the 2 inch
(5 cm) mark. Tape the pencil to
the table.
Empty the cups and do the test
again, but with the pencil placed
at 6 inches (15 cm) and 10 inches
(25 cm). How did the position of
the fulcrum affect the effort needed
to lift the load?
Place the pebble in the Load cup.
Add coins to the other cup, one by
one, until the Load cup is raised up.
Make a note of how many coins are
in the Effort cup.
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