Secrets of Lost Empires I—Colosseum
To discover how to use pulleys to change the direction of force.
- copy of "Reel Distances" student handout
- several meters (yards) of string
- two pulleys
- paper clips
- wooden laundry clips
- paper cups
A pulley consists of a freely turning wheel and a rope. The wheel is fixed to a
support and the rope runs over the wheel. Students can discover how to use
pulleys to change the direction of force (e.g., pulling a rope down to hoist a
flag up) in this activity.
Organize students into small
groups and distribute copies of the "Reel Distances" student handout and a set of materials to
Point out to students that the ancient builders had to be
remarkably inventive in their use of materials and tools to achieve their
engineering feats. Explain that each team must devise a way to send a note back
and forth across a distance, using only the materials provided. (See How to Make a Pulley below.)
Allow students to discover for
themselves how pulleys might be used for the challenge. When groups have
completed the challenge, have each group present its method to the class and
explain how group members came up with their design. Working with students,
develop ways to evaluate designs, noting that no one best design exists and
that different tasks require different designs.
How to Make a Pulley
Materials for each pulley
- one wooden spool
- wire cutters
- wire coat hanger
Cut a 25 cm (10 in.) length of wire from the coat hanger. Slide the wire
through a wooden spool. Allow one end of the wire to extend farther than the
other. Use pliers to bend the wire at right angles on either side of the spool.
Bend the short end of the wire around the other to secure the ends together.
Bend the long end into a hook.
Students' designs will vary. If students are having difficulty
understanding how a pulley can be used to change direction of force, have them
experiment with one pulley, noting how when they pull down on the string, the
object attached to the other end is lifted up. Some teams may design systems
that do not involve pulleys. These are valid inventions and provide an
opportunity to compare different designs and discuss the advantages and
disadvantages of a pulley.