Fundamental Forces in Nature to Know for AP Physics 1 (2025)

Fundamental forces shape our universe, governing everything from the motion of planets to the interactions of tiny particles. Understanding these forces—gravitational, electromagnetic, strong nuclear, and weak nuclear—helps us grasp the principles of mechanics and the behavior of matter.

1. Gravitational force

   • Attracts objects with mass towards each other.
   • Responsible for the motion of planets, stars, and galaxies.
   • Weakest of the four fundamental forces but has an infinite range.

2. Electromagnetic force

   • Acts between charged particles, causing attraction or repulsion.
   • Governs electricity, magnetism, and light.
   • Stronger than gravity and has an infinite range.

3. Strong nuclear force

   • Binds protons and neutrons together in atomic nuclei.
   • Operates at very short ranges (about 1 femtometer).
   • Strongest of the four fundamental forces.

4. Weak nuclear force

   • Responsible for radioactive decay and neutrino interactions.
   • Acts over very short distances (less than 0.1% of a proton's diameter).
   • Plays a crucial role in nuclear fusion processes in stars.

5. Newton's law of universal gravitation

   • States that every mass attracts every other mass with a force proportional to the product of their masses and inversely proportional to the square of the distance between them.
   • Mathematically expressed as F = G(m1*m2)/r².
   • Provides a framework for understanding gravitational interactions in classical mechanics.

6. Coulomb's law for electric forces

   • Describes the force between two charged objects as proportional to the product of their charges and inversely proportional to the square of the distance between them.
   • Mathematically expressed as F = k(q1*q2)/r².
   • Fundamental in understanding electric fields and forces in electrostatics.

7. Fundamental particles (quarks, leptons)

   • Quarks combine to form protons and neutrons; there are six types (up, down, charm, strange, top, bottom).
   • Leptons include electrons and neutrinos; they do not experience strong force.
   • Building blocks of matter, essential for understanding particle physics.

8. Force carriers (photons, gluons, W and Z bosons)

   • Photons mediate electromagnetic force; they are massless and travel at the speed of light.
   • Gluons are responsible for the strong force, binding quarks together.
   • W and Z bosons mediate the weak force, involved in processes like beta decay.

9. Range and strength of fundamental forces

   • Gravitational force: infinite range, weakest strength.
   • Electromagnetic force: infinite range, stronger than gravity.
   • Strong nuclear force: very short range, strongest force.
   • Weak nuclear force: very short range, weaker than strong force.

10. Conservation laws related to fundamental forces

• Conservation of energy: energy cannot be created or destroyed, only transformed.
• Conservation of momentum: total momentum before and after an interaction remains constant.
• Conservation of charge: electric charge is conserved in isolated systems.
• Conservation of baryon and lepton number: total number of baryons and leptons remains constant in reactions.