Catapult: Any machine that hurls a projectile. • “Kata” means downward. • “Peltos” refers to a small circular shield carried in battle. • “Katapultos” was taken to mean “shield striker.” A catapult is a machine that fires objects known as projectiles by first storing potential energy. When activated, the potential energy is quickly converted to kinetic energy. The kinetic energy creates an unbalanced force that can be used to accelerate the projectile. We typically think of a catapult as something that was used in the Middle Ages to destroy the walls of a castle. But Catapults have a very long history, dating long before the time of castles. The first catapults most likely originated independently in Greece and China around the 4th Century BC. However, unique catapult designs were developed and used by many different cultures over the centuries. The Trebuchet is probably the oldest type of catapult. It was invented either by the Chinese or by a culture located in the Middle East. Trebuchets were used mainly as lobbing machines to spread fire and diseased corpses, as well as a lot of solid missiles, over the walls of castles to rain down on the inhabitants. They were very effective! The next oldest type of catapult is the Ballista. The earliest form of the ballista is thought to have been developed for Dionysius of Syracuse, circa 400 BCE. Ballistae typically were used for lighter but more accurate projectiles, and could be easily modified to shoot either spherical or shaft projectiles, allowing their crews to adapt easily to prevailing battlefield situations in real time. Ballistae were even mounted on warships and used to hurl fire onto other ships. The Romans took the ballista, used it, and then improved in in the Roman way to create the Onager. Not much is known about how these machines really looked, but our best guess is something like this one. Onagers were used right up to the middle ages alongside the Trebuchet, when gunpowder and the cannon were invented and eventually replaced the catapults. Another example of a ballista. Modern aircraft carriers use catapults to launch aircraft on short runways. Catapult Challenge: Design and build your own marshmallow catapult! You may only use the following supplies in this challenge: •1 plastic spoon. •No more than 6 popsicle sticks (either size). •No more than 3 wooden dowels. •No more than 12 rubber bands. •Masking tape. •You must use a block or brick as a base. •Your catapult must be placed on the ground or on a table when launching. •2 Marshmallows. Objective: We will be testing accuracy, precision, and distance. Get started with a sketch right now! Accuracy refers to how close a measurement (observation) is to the expected or desired target value. The farther a measurement is from its expected value, the less accurate it is. All of the observations above hit the target, so they are all somewhat accurate. The ones near the bulls-eye are more accurate than the others, because they are close to the desired target. Precision refers to closeness of a set of repeated measurements (observations). The observations on the target above are closely clustered together; these observations are considered to have high degree of precision. However, since they are not in the bulls-eye, they are not very accurate! The observations on the target above are both precise (closely grouped) and accurate (close to the desired target).