Things You'll Need
Empty water bottle
Building a bridge out of toothpicks can make a fun and educational craft activity or science fair project. Kids learn the fundamentals of engineering and physics while employing math and science skills to construct a weight-bearing bridge out of toothpicks and marshmallows. Toothpick bridges can be constructed using as few or as many toothpicks as you would like.
Using four marshmallows and six toothpicks, construct a tetrahedron. Make sure to use the same size toothpicks throughout. Start by inserting three toothpicks into the bottom of one marshmallow. Press a marshmallow into each of the exposed ends of the toothpicks, then connect each of these marshmallows using another toothpick. You will need to make several of these to connect together to form your load-bearing bridge.
Measure the length you want your bridge to span, then measure the width of one of your tetrahedrons. Divide the length of the bridge by the width of a tetrahedron to determine how many tetrahedrons you will need to make.
Connect your tetrahedrons together with toothpicks. You can extend the bridge as far as you like, or connect tetrahedrons on top of each other for added strength.
Test your bridge's load-bearing strength by putting an empty water bottle on the middle of the bridge. Examine your structure for any weak spots and reinforce them by inserting more toothpicks. Remove the bottle, add a small amount of water and test your bridge again. Repeat this process, adding more water each time, until your bridge can support a full bottle of water.
A tetrahedron is a geometric figure that has four equal sides (equilateral triangles.) Add strength to your bridge by using several toothpicks to connect your marshmallows. Kids can also use gumdrops to make a toothpick bridge.