Each group needs:

• 20 plastic drinking straws (not the bendy type)
• scotch tape
• scissors
• measuring stick or ruler (or one for the class to share)

For the entire class to share:

• small paper cup
• 200-300 pennies (to use as weight)
• wooden support structure (or use two desks)
• balance (for weighing, or count the pennies instead of weighing)

To make the wooden support structure (see Figure 5; optional; may use two desks instead):

• two 7-inch (18-cm) pieces of 2 x 4 wood (for bridge abutments; use scrap 2 x 4s)
• 7 x 13-inch (18 x 33-cm) piece of .25-inch (.6-cm) thick wood (for water base between abutments)
• hammer and nails
• (optional) blue paint for the base of the support structure, to represent water under the bridge

Finished dimensions of the wooden support structure (optional; may use two same-height desks instead). Dimensions may vary from those below, but these particular dimensions can be made by using scrap 2 x 4s. The most important dimension is the inside length or span. The total length should allow for enough space to place the bridge on the "abutments."

• inside length "span" = 10 inches (25 cm)
• total length (span plus two abutments) = 13 inches (33 cm)
• abutment height = 3.5 inches (9 cm)
• abutment width = 7 inches (18 cm)