Undergraduate
  1. Classical mechanics  1.1. dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. projectile motion  1.1.4. Relative speed  1.1.5. Uniform circular motion  1.1.6. Non-uniform circular motion  1.1.7. Reference frames and transformations  1.2. Newton's Laws of Motion  1.2.1. First law of motion  1.2.2. Second law of motion  1.2.3. Third Law of Motion  1.2.4. Applications of Newton's Laws  1.2.5. Friction and its types  1.2.6. Free Body Diagram  1.2.7. Constraints and pseudo-forces  1.3. Work and Energy  1.3.1. work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy in classical mechanics  1.3.5. Conservative and non-conservative forces  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.4. Speed and collisions  1.4.1. Linear momentum  1.4.2. Conservation of momentum  1.4.3. Impulse and impact force  1.4.4. Elastic and inelastic collision  1.4.5. Center of mass and speed  1.4.6. Rocket Propulsion  1.5. Rotational motion  1.5.1. Torque and Angular Momentum  1.5.2. Moment of inertia  1.5.3. Rotational Kinematics  1.5.4. Rotational Energy  1.5.5. Rolling Motion  1.5.6. Precession and gyroscopic motion  1.6. Gravitational force  1.6.1. Newton's law of universal gravitation  1.6.2. Gravitational potential energy  1.6.3. Orbital mechanics  1.6.4. Kepler's laws of planetary motion  1.6.5. Gravitational field and potential  1.7. Fluid mechanics  1.7.1. Pressure and Pascal's Principle  1.7.2. Buoyancy and Archimedes' principle  1.7.3. Fluid Dynamics and Bernoulli's Principle  1.7.4. Viscosity and Poiseuille's law  1.7.5. Surface tension and capillarity  1.8. Oscillations and waves  1.8.1. Simple Harmonic Motion  1.8.2. Damped and driven oscillations  1.8.3. Coupled oscillations and common modes  1.8.4. Wave properties and types  1.8.5. Sound Waves and the Doppler Effect  1.8.6. Wave interference and superposition
  2. Electromagnetism  2.1. Electrostatics  2.1.1. Electric charge and properties  2.1.2. Coulomb's law  2.1.3. Electric field and electric potential  2.1.4. Gauss's Law  2.1.5. Capacitance and Dielectric  2.1.6. Electric dipole and potential energy  2.2. Electric circuits  2.2.1. Current and Resistance  2.2.2. Ohm's law  2.2.3. Kirchhoff's Laws  2.2.4. RC Circuit  2.2.5. AC Circuits and Reactance  2.2.6. Electric power and energy  2.3. Magnetism  2.3.1. Magnetic Fields and Forces  2.3.2. Ampere's Law  2.3.3. Magnetic dipole moment  2.3.4. Biot-Savart law  2.3.5. Magnetic Materials and Hysteresis  2.4. Electromagnetic induction  2.4.1. Faraday's Law  2.4.2. Lenz's law  2.4.3. Self and mutual induction  2.4.4. Transformers and Inductive Circuits  2.5. Maxwell's equations  2.5.1. Gauss's law for electricity  2.5.2. Gauss's law for magnetism  2.5.3. Faraday's law of induction  2.5.4. Ampere-Maxwell law  2.5.5. Electromagnetic waves
  3. Thermodynamics  3.1. Laws of Thermodynamics  3.1.1. Zeroth law of thermodynamics  3.1.2. First law of thermodynamics  3.1.3. Second Law  3.1.4. Third Law  3.2. Heat and work  3.2.1. Heat transfer (conduction, convection, radiation)  3.2.2. Thermal expansion  3.2.3. Heat engines and refrigerators  3.2.4. Carnot cycle and efficiency  3.3. Statistical mechanics  3.3.1. Maxwell–Boltzmann distribution  3.3.2. Entropy and Probability  3.3.3. Partition function  3.3.4. Fermi–Dirac and Bose–Einstein statistics
  4. Optics  4.1. Geometrical Optics  4.1.1. Reflection and Refraction  4.1.2. Mirrors and lenses  4.1.3. Optical Instruments  4.1.4. Fermat's principle  4.2. Wave optics  4.2.1. Interference in wave optics  4.2.2. Diffraction  4.2.3. Polarization  4.2.4. Coherence and holography
  5. Quantum mechanics  5.1. Wave–particle duality  5.1.1. Blackbody radiation in wave–particle duality in quantum mechanics  5.1.2. Photoelectric effect  5.1.3. Compton scattering  5.1.4. De Broglie wavelength  5.2. Schrödinger Equation  5.2.1. Time-independent Schrödinger equation  5.2.2. Particle in a box  5.2.3. Quantum Tunneling  5.2.4. Potential wells and obstacles  5.3. Quantum States  5.3.1. Wave function  5.3.2. Quantum operators  5.3.3. Heisenberg uncertainty principle  5.3.4. Angular momentum and spin
  6. Relativity  6.1. Special relativity  6.1.1. Lorentz transformations  6.1.2. Time expansion and length contraction  6.1.3. Relativistic energy and momentum  6.2. General relativity  6.2.1. Principle of Equivalence  6.2.2. Schwarzschild metric  6.2.3. Gravitational waves  6.2.4. Black holes and event horizons
  7. Solid state physics  7.1. Crystal structure  7.1.1. Bravais lattices  7.1.2. X-ray diffraction  7.1.3. Band theory  7.1.4. Phonons and lattice vibrations  7.2. Electrical and Magnetic Properties  7.2.1. Conductors, Semiconductors and Insulators  7.2.2. Superconductivity  7.2.3. Hall effect
  8. Nuclear and particle physics  8.1. Atomic Structure  8.1.1. Atomic Model  8.1.2. Nuclear binding energy  8.2. Radioactivity  8.2.1. Alpha, beta, gamma decay  8.2.2. Half life  8.2.3. Nuclear Fission and Fusion  8.3. Particle physics  8.3.1. Standard Model  8.3.2. Quarks and Leptons  8.3.3. antimatter  8.3.4. Fundamental interactions
  9. Astrophysics and cosmology  9.1. Stellar evolution  9.1.1. Star formation  9.1.2. Black holes and neutron stars  9.1.3. White dwarfs and supernovae  9.2. Cosmology  9.2.1. The Big Bang Theory  9.2.2. Dark matter and dark energy  9.2.3. Cosmic microwave background

Undergraduate → Nuclear and particle physics → Particle physics ↓


Fundamental interactions


In the vast field of physics, understanding the forces that govern the interactions of matter forms the basis of our knowledge of the universe. These interactions, called fundamental forces, are the basis of particle physics, which attempts to explain the nature of everything from the smallest particles to the largest cosmic structures. Let's look at these fundamental interactions, often called fundamental forces, in a simple and detailed way.

Four fundamental forces

There are four known fundamental forces in nature:

  1. Gravitational force
  2. Electromagnetic force
  3. Strong nuclear force
  4. Weak nuclear force

Gravitational force

Gravity is perhaps the most familiar force to us. It is the force of attraction between objects with mass. It keeps us bound to Earth and governs the motion of celestial bodies.

The gravitational force between two masses m 1 and m 2 separated by a distance r is given by Newton's law of gravitation:

F = G * (m 1 * m 2) / r 2

Where F is the gravitational force, and G is the gravitational constant. Although we experience it every day, gravity is the weakest of the fundamental forces, but it acts over large distances.

m 1 m 2

This simple diagram shows two masses being attracted to each other by the force of gravity.

Electromagnetic force

The electromagnetic force acts between charged particles. It is responsible for electricity, magnetism, and light. The force may be attractive or repulsive, depending on the charges involved.

The electromagnetic force is described by Coulomb's law:

F = k * |q 1 * q 2| / r 2

where q 1 and q 2 are charges, r is the distance between the charges, and k is the Coulomb constant.

Q1 Q2

This diagram shows two charges exerting a force on each other, demonstrating the electromagnetic interaction.

Strong nuclear force

The strong nuclear force is what binds the protons and neutrons together within the atomic nucleus. Despite the repulsive electromagnetic force between the positively charged protons, the strong force overcomes this to keep the nucleus intact. It is the strongest force but acts over a very short distance, roughly the size of an atomic nucleus.

Proton Neutron

The interactions between protons and neutrons within the nucleus are governed by the strong force.

Weak nuclear force

The weak nuclear force is responsible for the process of beta decay in radioactive atoms. It plays a key role in the nuclear processes that power the Sun and in the creation of elements in stars. Unlike the other forces, the weak force can change the type or "flavor" of particles.

An example interaction is the conversion of a neutron into a proton:

n → p + e + ν̅ e

where n is a neutron, p is a proton, e⁻ is an electron, and ν̅ e is an electron antineutrino.

N P

This diagram shows the transformation process caused by the weak interaction, where a neutron is transformed into a proton.

Interaction of forces

Understanding how these forces interact with one another provides insight into the fundamental workings of the universe. While each of these forces operates at different scales and strengths, they are crucial in maintaining the structure of matter as we know it.

Unified powers

One of the ongoing quests in physics is to unify these forces into a single theoretical framework. The electromagnetic and weak forces have been unified into the electroweak force, and researchers continue to develop theories that can unify the strong force with the electroweak force, leading to a Grand Unified Theory (GUT).

The ultimate goal is to unify all four fundamental interactions, including gravity, under a single framework, often referred to as the Theory of Everything (TOE).

Importance in the universe

Fundamental forces shape every aspect of the physical universe. Understanding these interactions helps scientists predict how matter will behave under different conditions, informing everything from the study of atomic structures to the dynamics of galaxies.

Earth Moon

The force of gravity is clearly visible in the Moon's orbit around Earth, a celestial dance driven by the infinite pull of gravity.

Conclusion

The four fundamental forces—gravity, electromagnetism, the strong nuclear force, and the weak nuclear force—are the primary means by which particles interact and form the backbone of the structure and behavior of the universe. By continuing to study these forces, physicists aim to uncover more truths about the universe, from the microscopic quantum level to the vast expanses of galaxies. As research progresses, so does our understanding of the deeper principles that govern existence.


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Fundamental interactions

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