What is the difference between a catapult and a trebucket?

Answer 1

A trebuchet is a large siege engine used to hurl missiles. To perform this task it uses a long arm and a sling to hurl projectiles. The sling is attached to the arm, and when the arm is moved by the release of a counterweight the sling is moved upward. Just after reaching the top of the arm's arc, the sling partially releases "throwing" the missile inside.

So the trebuchet uses a sling as the primary method of hurling its projectiles, the catapult simply uses an arm, which stops at a 90 degree angle while the projectile on board begins its journey to the target.

Mechanically, a trebuchet is a type 1 lever (fulcrum in the center, load on one end, force on the other). A catapult is a rod pushed through a spring, which uses torsion as the force.