Catapult Buy From Art.com Catapult Activity We typically think of a catapult as something that was used in the Middle Ages to destroy the walls of a castle as in the poster shown here. But Catapults have a very long history dating long before the time of castles and they were developed and designed in many different ways by many different cultures over the centuries. What is a catapult? The general definition is that a catapult is a machine that stores energy then quickly releases the energy to fire a projectile. To be a catapult the machine generally has to be too large for a person to carry. If we just used the storage and release of energy to define a catapult then a longbow would also fit this definition. So the size of the machine is important. How did catapults develop? Catapults are an offshoot of the Crossbow. Over time crossbows got larger and larger. They went from being a hand-held weapon to something called the Belly-Bow which were so large they had to be braced against a knight's belly. From there they got even larger and became something called a stand crossbow where they were mounted on stands. Eventually they got large enough to be defined as something in their own right and no longer crossbows. This size change also brought about changes in how they operated. When did the first catapults appear and where? The earliest writings of catapults were that they originated in China around the 3rd and 4th Century BC and this type of catapult was much like a big crossbow. They stood around 8 feet tall. The illustration here shows this early type of catapult. You can see by the design that it is a natural extension of the crossbow. It is pretty much a very big crossbow! But the unique development that turns it into what we consider to be a catapult is the swinging arm. This is mounted on a pivot and thus we have a catapult. The crossbow string itself is not used to fire the projectile; it is used to move the arm which holds the projectile.
Vocabulary: acceleration: an increase in rate of change balanced force: two forces that are equal in size and opposite in direction catapult: an engine that provided medieval artillery used during sieges; a heavy war engine for hurling large stones and other missiles elastic energy: the energy which causes or is released by the elastic distortion of a solid or liquid kinetic energy: maximum kinetic energy is when an object is at the mean position and minimum at the extreme position mass: the property of a body that causes it to have weight in a gravitational field Newton s Laws of Motion: three physical laws that form the basis for classical mechanics. They are: o 1) In the absence of a net force, a body either is at rest or moves in a straight line with constant speed. o 2) A body experiencing a force F experiences an acceleration a related to F by F = ma, where m is the mass of the body. Alternatively, force is equal to the time derivative of momentum. o 3) Whenever a first body exerts a force F on a second body, the second body exerts a force -F on the first body. F and -F are equal in magnitude and opposite in direction. potential energy: maximum potential energy is when an object is at the extreme position and minimum at the mean position trebuchet: a trebuchet or trebucket is a siege engine that was employed in the Middle Ages either to smash masonry walls or to throw projectiles over them unbalanced force: an unopposed force that causes a change in motion
Part I: Designing your catapult Develop a set of blue prints for the construction of your catapult. Your blueprint needs to show an accurate representation of your design as shown from a top view and a side view. Below are two examples of what to do. Remember, just because you sketch a particular design, doesn t mean that you have to build or commit to that design. As you begin the process, you may find that you need to tweak certain elements of your design based on the materials you are given and functionality. Remember that you can build your device however you would like, but it must be free standing. Thinking outside of the box is a BIG PLUS!!! Remember that your blueprint is what you want your catapult to look like as well as how it will function. As you begin to build your catapult you may find that you need to change various parts in order for it to function. That is fine. YOU WILL NOT BE ALLOWED TO BEGIN CONSTRUCTION ON YOUR CATAPULT UNTIL YOU HAVE SUBMITTED YOUR BLUEPRINTS! **Blueprint = 20 points (10 for top view, 10 for side view)** When constructing your catapult you need to keep in mind the overall purpose: Efficiency o How difficult is your catapult to load and release? o How quickly can your catapult be reloaded? Distance o What angle do you need your catapult to release your marshmallow to obtain the maximum distance? Accuracy o Can you adjust your catapult s tension to launch your marshmallow different distances? For your catapult to function correctly during this activity, it must include a trigger mechanism to release the launching arm. You cannot hold the launching arm in the ready position. You must have a release switch.
Part II: Construction of your catapult All students will have the following materials available for use: Shoe box (various sizes) Mouse trap (1) Rubber bands (various sizes, maximum of 4 per group) Clothes pins (2 per group) Duct tape (2 feet per group) Masking tape (3 feet per group) Wooden rods (4 per group) Craft sticks (4 large and 10 small per group) Paper clips (2 large, 2 small per group) String Glue Plastic spoon (one per group) Straws Springs Fishing weights Fishing string One jumbo sized marshmallow for launch You are not required to use all of the available materials to build your catapult. You will not be allowed to bring in any extra items for use in building or launching your catapult. Any team found to have extra items will be disqualified from the launch and will receive a grade of zero for the entire project.
Assessment: Each student will write a paragraph that answers the following questions: What was your group attempting to achieve with its catapult design? How did the catapult set the marshmallow in motion? Which challenge did your catapult meet best, accuracy or distance? What could you have done to make the catapult better? What helped the catapult work as well as it did? What did this activity teach you about motion and forces? Top view drawing of catapult design = 10 points Side view drawing of catapult design = 10 points Catapult launch distance = 6 Construction participation = 6 Launch participation = 6 Summary paragraph = 6 TOTAL PROJECT POINTS = 44 6 4 2 0 Catapult successfully Catapult successfully launched a launched a marshmallow at least 3 marshmallow at least 1 feet foot Catapult successfully launched a marshmallow at least 5 feet. Actively participated in the design and construction of the catapult. Actively participated in the launching of the catapult Answered all six questions in a complete and thoughtful paragraph Answered 4-5 of the questions in a complete paragraph. Answered 2-3 of the questions-paragraph not complete Catapult did not successfully launch a marshmallow at least 1 foot Did not participate in the design or construction of the catapult. Did not participate in the launching of the catapult. Answered 0-1 of the questionsparagraph incomplete or did not do