I have always thought that all of "Classical Mechanics" can be explained with Newton's Laws and a few force equations (e.g., gravitational and Coulomb). In particular, the concepts of energy and torque are convenient but not necessary. If this is true, then can you explain with Newton's Laws - without talking about energy or torque - how a lever "multiplies a force"? For example, consider a see-saw that is balanced (and not rotating) because the child who weighs half as much sits twice as far from the fulcrum. Is there a model that shows how the intermolecular forces are transmitted down the board in such a way that the board pushes upward with twice the force on the heavier child?