You can make a pencil stand up vertically using only four strings for support. Once you’ve done this activity, you will use the pencil as a stand
to balance a triangle in Activity 2.
Work with a partner.
1. Begin with a sharpened
pencil. Tape four long strings
to the pencil near its point.
The ends of the strings
should be equally spaced
around the pencil and should
be the same distance from
the point.
3. Have one person stand the pencil
upright on a piece of cardboard by
extending two of the strings on opposite
sides. Make sure the strings are taut.
Now the other person should tape the
strings in place on the cardboard.
2. Pull the strings taut and
cut them so that they are
all the same length. They
should extend about one
inch beyond the end of
the pencil.
4. Repeat Step 3 with the remaining
two strings. Once you and your partner
are done, the pencil should stand up
by itself.
5. Given that the four strings are the same length, explain how you know that the pencil is
perpendicular to the cardboard.