Physics Behind the Trebuchet: Forces

FORCES:

Because the sling side of the lever arm is longer than the counterweight side, the sling side has to move faster than the counterweight side of the lever arm when the trigger is released. The sling works because of tension. At the beginning, both the fixed and sliding rope of the sling have tension, but at some point in its path, the sliding rope decreases in tension and continues to decrease until the rope slides off. The sling itself experiences centripetal acceleration, and it has to move faster than the sling side of the arm, therefore much faster than the counterweight side of the lever arm, when the trigger is released. Increasing the length of the arm and the length of the sling would increase the trebuchet's range.

Centripetal Force(Fc): This is the force acting on the sling that causes it to move in a circular manner until released.
Acceleration(a): As gravity affects the lower side of the arm, the upper side experience acceleration.
Gravity: Gravity is what pulls the counterweight down, and thus moves the arm.
Normal Force(Fn): The force that the ground exerts upon the trebuchet.

"Trebuchet Physics." Trebuchet Physics. Real World Physics Problems, n.d. Web. 20 May 2014. <http://www.real-world-physics-problems.com/trebuchet-physics.html>.