The physics principles that are used are newtons laws. The concepts used are that the gravity vector always goes to the center of the earth and that is always the ground so the weights will always fall down once released so the weights will fall forcing the atom upward in to the air. The trebuchet also works by the sling being released from the end of the paper clip which changes the angle the atom is released at. Factors that we can change about our trebuchet are the angle of release and counter weight.
Pics of our cardboard trebuchet.
