CONSTRUCTING
FIRST-CLASS LEVERS
PHYSICAL SCIENCE / EASY LEVEL
Introduction
A machine makes work easier by doing one of the following: moving
the force from one location to another, changing the direction of
the force involved, increasing the amount of force, or increasing the
distance or speed of the force. There are six simple machines that
make up all complex machines. The first simple machine is the lever.
A lever is a rigid bar that moves around a fixed point, or fulcrum.
There are three classes of levers, determined by the location of the
fulcrum, effort force, and resistance force (the object you want to
move). In a first-class lever, the fulcrum is between the effort force
and the resistance force. In this experiment, you will learn about
first-class levers.
Time Needed
30 minutes
What You Need
✎
✎
✎
✎
✎
✎
✎
string
broom handle
2 or 3 large potatoes
plastic bag, such as from a grocery store
wooden rolling pin
duct tape
tall, plastic wastepaper basket
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Safety Precautions
Please review and follow the safety guidelines at the
beginning of this volume.
What You Do
1. Use the duct tape to tape the rolling pin to the center of the
broom handle (Figure 1). The rolling pin will be the fulcrum.
duct tape
broom handle
rolling pin
Figure 1
2. Place the wastepaper basket upside down.
3. Place the rolling pin/broom handle on the wastepaper basket
(Figure 2).
broom handle
on rolling pin
upside-down
wastepaper basket
Figure 2
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4. Place the potatoes in the plastic bag. Lift the bag of potatoes,
and note how much effort it took to lift the bag.
5. Tie the plastic bag to one end of the broom handle using the
handholds of the bag (Figure 3).
broom handle
on rolling pin
plastic
bag
upside-down
wastepaper basket
Figure 3
6. Push down on the other end of the broom handle. Note how
much effort it took to lift the bag of potatoes using your “lever.”
7. Place your hands halfway between the end on which you were
pushing and the fulcrum (rolling pin). Note the amount of effort
it took to lift the potatoes.
8. Slide the bag of potatoes halfway between the end to which they
were attached and the fulcrum.
9. Push down on the opposite end of the handle. Note the amount
of effort it took to lift the potatoes.
Observations
1. With which placement of your hands and the bag
of potatoes was it easiest to lift the potatoes?
2. From where did the effort force come?
3. What served as the resistance force?
4. What items in a playground might be levers?
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JUNIOR SCIENCE EXPERIMENTS ON FILE,TM VOLUME 2
1.0 Safety Guidelines (page 1)
1.0 SAFETY GUIDELINES
GENERAL
get your teacher’s permission for experiments performed
• Always
at school, and your parent’s permission for experiments performed
•
•
•
•
•
•
•
•
at home, before attempting any experiment.
Read all instructions for an experiment several times before
starting the experiment, and follow the directions exactly as they
appear in this volume.
If an experiment requires adult supervision, do not perform the
experiment unless you have an adult supervising you the entire
time you are performing the experiment.
Wash your hands before the start of, and after, each experiment
you perform.
Keep your work area clean.
Never eat or drink while performing a lab experiment. Never taste a
substance used in an experiment unless you are told that it is safe
to do so.
Be aware of the location of equipment that you may need in an
emergency, such as running water, an eyewash if you are at school,
a fire extinguisher, etc.
If you are going outside, make sure you have teacher or parent
permission to go. Take a buddy with you and dress appropriately for
the weather. Make sure you or someone who accompanies you is
familiar with the area, and bring along a first-aid kit in case of an
emergency.
Never look directly into the Sun.
CHEMICAL SAFETY
wear goggles when working with chemicals, such as acids
• Always
and bases, and near heat sources like flames. If at all possible,
•
•
•
avoid wearing contact lenses when working with chemicals.
If any substance gets into your eyes, notify an adult (e.g., your
teacher or parent) immediately and flush your eyes with running
water for at least 15 or more minutes. Do not mix chemicals unless
you are told to do so by a teacher or parent.
Never touch, taste, or smell chemicals unless instructed to do so.
Keep chemicals in closed containers when they are not in use.
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1.0 Safety Guidelines (page 2)
JUNIOR SCIENCE EXPERIMENTS ON FILE,TM VOLUME 2
of all used chemicals properly. Do not pour any chemicals
• Dispose
or solids down the drain unless instructed to do so.
safety gloves and a plastic apron when handling chemicals. If
• Use
any chemicals spill on your skin, rinse it with running water for at
•
•
least 10 minutes, and notify your teacher or parent immediately.
Take precautions to avoid spilling chemicals. If a chemical spills on
any surface, notify your teacher or parent immediately to assist with
clean-up.
Exercise caution when using sharp instruments such as knives or
scissors. Always cut away from yourself, not toward yourself. If you
are cut, notify your teacher or parent immediately.
GLASSWARE
glassware when you are finished with the experiment.
• Clean
careful when using glassware. If a piece of glassware breaks,
• Be
have an adult assist you in clean-up to avoid injuries due to broken
glass. Never use broken or damaged glassware.
FIRE SAFETY
not heat glassware that is not completely dry. Do not pick up
• Do
hot glassware without heat-resistant gloves or tongs.
heating glassware, keep it away from yourself and from
• When
others.
not heat anything unless instructed to do so by a teacher or
• Do
parent.
not heat substances in a closed container.
• Do
an experiment, make sure that all heating sources are turned
• After
off and that all flames have been put out.
not reach across such heating sources as flames.
• Do
back long hair. Do not wear clothing with loose sleeves, scarves,
• Tie
bows, ties, or anything else that may hang into a fire. Do not wear
long earrings.
ELECTRICAL SAFETY
not touch electrical equipment if your hands are wet.
• Do
not plug many electrical devices into one outlet or use an
• Do
extension cord.
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