Complex sentence: In classical physics, time evolution of a collection of rigid bodies is governed by certain laws, which in their most rudimentary form, express the relationship between forces acting on the bodies and their acceleration given by Newton's laws of motion.
Split into simpler sentences: In classical physics, time evolution of a collection of rigid bodies is governed by the principles of classical mechanics. In in their most rudimentary form, these principles express the relationship between forces acting on the bodies and their acceleration given by Newton's laws of motion.