What are the differences among a catapult a trebuchet and a ballista?

Answer 1

A trebuchet is a counterweight powered artillery piece. A huge counterweight at one end of a pivoted arm drops under gravity, throwing a missile (such as a lump of rock or iron) into the air. A sling arrangement is often used on the end of the arm as well to provide additional acceleration for the missile. It was rare, but not unheard of, for a basket design, much like a catapult's, to be used.

A Ballista is a Roman siege weapon that can be loaded with a large stone ball or a large bolt (a large, heavy arrow).

It's maximum effective range is over 500 yards.

It is extremely accurate, especially at close range.

A Ballista bolt can impale several soldiers and a stone would cause absolute carnage in enemy ranks, as you could imagine.

So it was effectively a ranged weapon used during battle to cause mass enemy casualties.

A catapult though is diffrent from a trebuchet because it does not pivot to throw its payload. The arm goes down and then stops at a certain point when firing.