What is a Trebuchet?
A trebuchet is a historical ballistic mechanism used
during the middle ages. From a dynamics perspective, the trebuchet
is a triple pendulum mechanism. A diagram of the mechanism is shown
below. The mass m3 is the projectile located at the end of a sling
of length c. The main arm of length L and mass m1 drives the projectile
through the lowering of a counterweight of mass m2. Unlike a catapult,
this counterweight was often designed in the form of a pendulum as shown
below, thus optimizing the transmission of potential energy of the counterweight
to the kinetic energy of the projectile..
Figure 1. Diagram of a triple pendulum mechanism. 
