Students will compare how much force is needed to lift objects without a pulley, then how much force is needed with a pulley.
- Can with a plastic lid
- 1 or more rubber bands,
not too strong
- 2 matchsticks or
- Weighted mass (e.g.,
1/2” galvanized pipe
joint or large metal nuts,
bolts, washers, etc.)
- Poster board cut to the
dimensions of the can
- Opaque tape (optional)
Lift The Load
For each group:
- 2-2 1/2 foot lengths of
- Thread spool
- 2 new pencils
- 4-8 oz. paper cups
- 12-4” pieces of string
- 6” piece of string
- Weights (30 of each):
flat or round marbles,
pennies, beads, jumbo
- Simple Machines (Starting with Science Series), by Deborah Hodge;
- How Can I Experiment With…? Force and Motion, by Cindy
- Science in Seconds for Kids: Over 100 Experiments You Can Do in
Ten Minutes or Less, by Jean Potter; ISBN 0-471-04456-3
- Science Experiments with Simple Machines (Science Experiments
Series), by Sally Nankivell-Aston; ISBN 0-531-14579-4
Background for Teachers
A simplified definition of work is to make an object move or to
change it’s motion. Simple machines are devices that make work easier.
All simple machines transfer force. Some change the direction of force,
while others change the strength of the force. Still others change both the
direction and the strength. Most simple machines make work easier by
allowing you to use less force over a greater distance to move an object.
Some machines make work easier by allowing you to move things farther
and/or faster. In these machines, a larger force is required, but over a
It would be preferable to include more than one pulley system, but
due to the nature of the activity, it would involve a considerable amount
of time for the students to attempt to build a more complex pulley
system. This activity is adequate as a simple comparison between
working with and without a pulley.
The invitation to learn is an example of a wheel and axle.
Intended Learning Outcomes
1. Use Science Process and Thinking Skills
2. Manifest Scientific Attitudes and Interests
3. Understand Science Concepts and Principles
4. Communicate Effectively Using Science Language and Reasoning
Invitation to Learn
Students observe as you place what seems to be an ordinary can on
a table. Tell them to watch its movements very carefully. Begin with
the can sitting on the table. Focus attention to the fact that it is still
and will not move by itself. Next, roll the can gently. It will return to
you. Have the students try to figure out why the can returns when it is rolled.
You may explain it and show what is happening, or leave it a
Explanation: The can stores energy in the rubber band because the
weight remains in position as the rubber band twists. When the
can stops rolling forward, the stored energy in the twisted rubber
band propels the can in the opposite direction.
To make a returning can:
- Make two holes in the lid and two in the bottom
of the can to
attach the rubber bands. Attach the weight to the rubber bands,
then run the rubber bands through the holes in the bottom and the
lid of the can.
- Secure rubber bands by running a match stick or splint
the loop in the ends. You may want to cover the ends with tape so
the rubber bands cannot be seen.
- Practice rolling the can. If you roll
it too hard, the rubber bands
will allow the weight to spin, and it won’t work properly.
Explore how a wheel and axle work to make work easier. Will a
wheel and axle make homework easier? Probably not, but it does make
some mechanical work easier. Prove this by learning how a wheel and
axle work as part of another simple machine called a pulley. Compare
how much force is needed to lift objects without a pulley, then how much
force is needed with a pulley.
Model for the students and explain how to build the system:
- Assign one
student from each group to gather materials.
- Tape the new pencils to a
desk or table top with most of the
length extending over the side.
- In each cup, tape three 4-inch strings
around the outside of the
cup, then tape them together at the tips to form a three-armed
handle for the cup.
- Take one length of ribbon and attach each end to a
running the ribbon through the handle, folding it back to form a
small loop, then tape it. Hang this first set of cups over one
- Take the piece of string and thread it through the hole in
spool and tie it to make a loop. Put the loop over the second
- Attach one end of the remaining ribbon to a cup the same as
above. Thread the other end over the spool as it hangs from the
pencil, then attach it to the last cup.
- Using the cups without the spool,
put items in one cup. Predict
how many it will take to lift the cup off the ground and lift the
cup to the top. Explain that they will compare this data, using the
same items in the cups attached to the pulley.
- Show the students how to
complete the Lift the Load worksheet.
Model how to predict, record the prediction, how to add items,
recognize the actual count, and how record it. Model how to work
together and take turns.
Assist groups as necessary in constructing pulley systems and
beginning the experiments.
Have students compare the force needed to lift their items with and without
the pulley system. Log the results on the Lift the
Load worksheets and draw conclusions about how pulleys make
mechanical work easier using the wheel and axle.
- Students devise their
own pulley system and demonstrate for the
class. Even if it fails, they will learn in the process and recognize
the scientific process involved in an invention process.
the vocabulary of Math Standard V-2a (Probability)
when predicting how many items it will take to lift the cup off the
ground and lift it all the way to the top. For example, "It is likely
that it will take five marbles to lift the cup of five marbles off the
ground. It is not likely that only three marbles can lift the cup."
- You may choose to use this lesson as a demonstration only and
have students respond verbally or by drawing pictures to record
predictions and actual results.
- Students can make and demonstrate
their own returning can to
family members and teach them how it works. Provide them with
a list of necessary materials and assembly instructions.
- Students make their
own pulley systems at home and compare the
force needed to lift various household items.
- Class discussion and responses on the Lift the Load worksheet
are the primary form of assessment.
- Active participation with the group in building, discussing, and experimenting
is another form of assessment.
Joritz-Nakagawa, J. (1992). Spencer Kagan’s Cooperative Learning Structures.
2nd Peace as
a Global Language Conference Proceedings & Supplements, 7-8.
This paper discusses Spencer Kagan’s approach to cooperative
learning, which is structured peer interaction and collaboration to achieve
a purpose. There are countless structural possibilities that can be used in
any learning situation. The article gives examples of some structures. It
also mentions structuring activities to involve multiple intelligences to
make learning meaningful and accessible to students.