Construct a catapult - middle years

One of the projects is to work as part of a team to construct a working model of a catapult. The catapult must be able to throw a light object such as a marshmallow or a table tennis ball a considerable distance, as accurately as possible.

To begin, here is some interesting information about catapults.

In mediaeval times, before guns had been invented, huge catapults were used as weapons to throw heavy objects such as rocks at the enemy. There were various designs, but these large weapons all used the principles of simple machines. They used potential (stored up) energy which, when suddenly released, would propel the missile.

Sometimes this energy would come from a large falling weight, and sometimes from the elastic energy stored up in a huge cross-bow type of machine. To load the catapult ready for firing, the large weight would have to be lifted to the top of the machine, or the cross-bow arms drawn back into the loaded position. This would have required considerable work, so it was probably done using simple machines such as ropes and pulleys to gain a mechanical advantage and make the job easier. Then the machine would be ready to fire.

When the catapult was fired, this stored up energy would be transferred into movement (kinetic energy). The large weight would suddenly fall, or the arms of the cross-bow would straighten. This sudden release of energy would throw the rock at the enemy. Often simple machines such as levers would be used to magnify the distance. (This is a bit like casting a fishing line and hook with a fishing rod, or hitting a ball with a hockey stick. A large force applied for a smaller distance moves a smaller load for a larger distance).

If you would like to construct a catapult as an EngQuest project, why not ask your teacher?