This is an optional exercise for teachers who want to include a math and science lesson in their unit. Students design, build and test catapults for accuracy and power. The challenge is to hurl a predetermined object a required distance to hit or knock down a targeted structure. 

Plays sometimes use special-effects props. These props typically look real from the audience's perspective; however they may be smaller in scale, or function differently than the real thing, - like a knife that dribbles "blood" when the blade is depressed or a castle wall that collapses during a battle scene.

In medieval times, catapults were one of a number of war devices used in a castle siege or attack. Sometimes an army would surround a castle, keeping food and other supplies from entering, and then wait for the inhabitants to starve or give themselves up. Since that could take years, soldiers would attack with machines, such as catapults. Catapults could knock down walls or hurl objects over castle walls. 

The Mental Joust: What are special-effects props? How can we build our own special effects prop? What design elements are required for a catapult to hit or knock down a target? How do we measure the power and accuracy of our catapults?

Time: 45 minutes

Suggested Materials: cardboard boxes, cardstock, rubber bands, cardboard tubes, tape, glue, toothpicks, craft sticks, plastic spoons, staples, flexible rulers, large marshmallows, ping-pong balls, tape measure, scissors, hole punch, felt tip markers, Book of Days. 

Worthy Words: catapult, siege

Procedure:

1. Does anyone remember what a prop is? Not all theatrical props work like the real thing. Sometimes they only look real. Can anyone think of an example?
2. We are going to be building our own special-effects prop - a catapult. Does anyone know what a catapult is? What is its function? Show photographs of catapults. See resource suggestions at the end of this lesson. There are basically two ways catapults work. Can you explain how they might work (by counter weight or by tension)?
3. Ask students to decide how they will test their finished catapults. What should be our catapults' target? What object should our catapults hurl? A ping-pong ball or a marshmallow would work. How far away should our catapults be from the target? How many tries should be given to each catapult?
4. Divide the class into small groups. Give each group the same variety of supplies to work with. Ask students to discuss various ways they could build a catapult. Students build their designs. If necessary, below is an example of how to build a simple but effective catapult; however, it is preferable for students to explore ways to build their own designs.
5. Ask each group to describe how their design works. Test each design given the parameters the students decided upon. Was your catapult powerful, but lacking accuracy? Was your catapult accurate, but lacking power? 
6. Ask students to sketch their design and record what they learned about their catapult's capabilities (or lack of capabilities) in their Book of Days. 

Materials: A sturdy and narrow cardboard box (such as a shoe box), two rubber bands, a plastic spoon, scissors, Exacto knife (optional), masking tape, a ping-pong ball or marshmallow.

1. Cut two vertical slits about 3/4 inch down and 1/2 inch apart along the top and near the center of the long sides of a cardboard box with scissors. (Figure 1.)
2. Cut two more vertical slits below the original ones in the center of the long sides of the box. Cut one additional horizontal slit connecting the bottoms of the two slits you just made, so the cuts form u-shaped slits. (Figure 2.)
3. Slip the ends of a rubber band around each of the u-shaped slits so the rubber band is stretched across the box. Tape the rubber band securely in place. (Figure 3.)
4. Slip the ends of a second rubber band around the slits in the top of the box and tape the ends of the rubber band. (See figure 4.)
5. Place the handle of a plastic spoon through the top rubber band and twist it around several times until the spoon is held securely in the center of the box. (Figure 5.) Make sure that the direction you twist creates a forward tension on the concave side of the spoon.
6. Place the handle of the spoon against the lower rubber band to create tension and a springing action. (Figure 6.)
7. Pull back the spoon, place a ping-pong ball inside, and release!

Exhibit Connection: 
See examples of "fake" props (props that look like the real thing from a distance, but are made out of styrofoam and other materials) at The Children's Museum.

References & Resources:

Gravett, Christopher. Eyewitness Books: Knight. New York: Alfred A. Knopf, 1993.

Jordan, William Chester. The Middle Ages: A Watts Guide for Children. New York: Grolier Publishing, 1999.

Macdonald, Fiona, How Would You Survive in the Middle Ages? New York: Franklin Watts, 1995.