Electricity and magnetism, like gravity, exert long-range forces. We will study electric and magnetic forces in detail in Part VI. For now, it is worth noting that the forces holding molecules together—the molecular bonds—are not actually tiny springs. Atoms and molecules are made of charged particles—electrons and protons—and what we call a molecular bond is really an electric force between these particles. So when we say that the normal force and the tension force are due to “molecular springs,” or that friction is due to atoms running into each other, what we’re really saying is that these forces, at the most fundamental level, are actually electric forces between the charged particles in the atoms.