Topic overview

Start with the big picture

The lesson begins with force, its SI unit and dimensions, and Newton’s second law, then distinguishes balanced forces from a nonzero net force. It connects force to work through displacement and compares conservative forces, such as gravitational and electrostatic forces, with dissipative forces such as friction and viscous drag. The topic then turns to applications in physical chemistry: interatomic interactions and potential energy, pressure, rotating reference frames, and the quantum-mechanical perspective. Bond restoring forces and force constants link molecular potential energy to vibrations, while molecular geometry optimization uses calculated forces. Together, these ideas provide a framework for interpreting force across macroscopic mechanics and molecular systems.