Catapult

An essential feature of medieval warfare was siege weapons. These include the siege tower, covered ladders, and the catapult, perhaps the most fearsome weapon of them all. From a safe distance, beyond the range of the archers in the castle, the catapult could fling rocks high into the air so that they crashed down onto the walls causing them to crumble. The catapults could also be used to throw burning bales of straw to set the wooden and thatched buildings in the castle grounds on fire. There were several different types of catapults. Some used large blocks of stone as a counter weight to cause a long arm to fling rocks onto and over the castle walls. Others used the energy stored in twisted rope for the same effect.

Your task is to design and build a realistic catapult that can throw small rocks as far and accurate as possible.

Motivation
To help in the design process, instruct the students to look at the picture on the front of the unit and read the accompanying text.
Alternatively, let the students search the Internet to learn more about the appearance, shape and form of ballistas, mangonels and trebuchets.
Discuss the constraints and functions the ancient engineers would have had to take into account.

Note: You are advised not to share this image with students.

While the activity is in progress, encourage the students to relate their knowledge, skills and understanding to the task at hand by asking:

How will your catapult work? Will it use counterweights, twisted string or rubber bands?
What sort of structure will you use to support the throwing mechanism?
How will you ensure that the throwing action does not cause the catapult to fall over?
How will you ensure that the catapult can be easily moved from place to place?
What will you use for ammunition?

When the activity is almost finished, encourage the students to reflect on both the product that they have produced and the processes they have used by encouraging the students to:

Carry out tests to evaluate the performance of the catapult:

• What is its range?
• What is its accuracy?
• What is its consistency?

Record their design by drawing it or taking digital photos of it.
Add notes describing the way the model works and how this might be improved to get a better performance.
Describe how to ensure safe use of the model.
Write briefly on what went well in their design task and what they could have done to improve it.

Look at:

Beam Balance (Building Instructions)

Levers Principle Models (Building Instructions)