Connections to Technology
The pendulum weight is called a bob, and the time
that the pendulum takes to swing back and forth one
time (for example, left to right, and back to the right
again) is called a period. These are terms that children
will quickly acquire if teachers model them while
children explore the pendulum.
A magnet is an object that produces an invisible
magnetic field, a force that pulls other ferromagnetic
materials (chiefly iron) toward it. It is incorrect to tell
children that magnets attract all metallic objects,
because in most cases this is true only for materials
that contain iron. Notice that magnets will not pick up
an aluminum pop-top, a silver necklace, or current
American coins, although these objects are made of
metal. Kindergarten and older preschool children
may be interested in the book What Makes a Magnet?
by Franklyn M. Branley.
Two areas of mathematics are involved in the inves-
tigations in this STEM center: number concepts and
measurement. To integrate number concepts, teach-
ers can help children count the number of periods
before the pendulum comes to rest. Also, if teachers
clap a steady beat along with the children and count
the number of claps per period, children will discover
that even though the arc of the pendulum gets smaller
and smaller, the number of claps per period remains
the same. Teachers can also help children measure
the distance between the pendulum bob (magnet)
and the paper clips, as previously described.
During their life experiences, children may have
noticed the wrecking ball on a crane that is used to
knock down buildings. This is an application of the
properties of a pendulum to achieve an engineering-
related purpose. The wrecking ball is the bob of the
pendulum. Children’s books, such as Bam, Bam, Bam
by Eve Merriam and Machines at Work by Byron
Barton, document this process.
Comments and Questions
to Support Inquiry
• Why does the pendulum pick up so many more
paper clips from the middle of the tray?
• Here’s another magnetic wand. See if it will pick
up any paper clips from the edge of the tray. Does
it? Then why doesn’t the magnetic wand on the
pendulum pick up the paper clips on the edge?
• Which paper clips don’t get picked up by the
magnet? • I agree that the magnet doesn’t attract the plastic
paper clips, but this paper clip got picked up, and
it looks like plastic.
• Can you figure out how close the magnet has to be
to this paper clip before it will pick it up?
• Let’s count how many claps it takes for the pendu-
lum to go back and forth each time.
Adults often tell children that magnets are
attracted to objects made of metal. This is inac-
curate. Magnets are mainly attracted to objects
that contain iron.
ST E M lE aR n I ng c E n T E R S