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How does a catapult work?

Though the definitions for types of catapults vary, each shares this goal: to hurl an object through the air. There are are three primary technologies that fall into the "catapult" category.

1. The catapult: the winched-down bucket that people normally think about when they hear the word "catapult".

2. The ballista is a very large crossbow .

3. A trebuchet is a weighted beam that swings a sling carrying the projectile .

Both catapults and ballistas work by storing tension either in twisted ropes or in a flexed piece of wood (in the same way an archery bow does, but on a larger scale).

A trebuchet tends to be easier to build because it consists simply of a pivoting beam and a counterweight that rotates the beam through an arc.

Catapults can launch things a fair distance -- 500 to 1,000 feet (150 to 300 meters) is common. It is surprising how much energy they can store. The gears are important, because they create a winch. The winch allows a person to put a great deal of energy into the catapult over a period of time. Then all of the energy releases at once, throwing the projectile.