Introduction to Physics: Core Concepts

• Physics is a natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force.
• Physics is one of the most fundamental scientific disciplines, and its main goal is to understand how the universe behaves.

Core Concepts

• Mechanics deals with the motion of bodies under the action of forces, including statics (bodies at rest) and dynamics (bodies in motion).
• Thermodynamics deals with heat, work, and energy, and the relationships between them; includes the study of the laws of thermodynamics, which govern the behavior of energy at the macroscopic level.
• Electromagnetism deals with the interactions between electric charges and magnetic moments and includes the study of electric fields, magnetic fields, and electromagnetic waves (light).
• Optics is the study of light and its behavior, including reflection, refraction, diffraction, and interference.
• Quantum Mechanics deals with the behavior of matter and energy at the atomic and subatomic level and introduces concepts such as wave-particle duality and quantization.
• Relativity includes special relativity (dealing with the relationship between space and time) and general relativity (dealing with gravity as a curvature of spacetime).

Mechanics

• Kinematics describes motion without considering its causes and includes displacement, velocity, acceleration, and time.
• Dynamics relates motion to its causes, particularly forces.
• Newton's laws of motion are fundamental.
  • First Law (Inertia): An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by a force.
  • Second Law: Force equals mass times acceleration (F = ma).
  • Third Law: For every action, there is an equal and opposite reaction.
• Work is the transfer of energy.
• Kinetic energy is the energy of motion (KE = 1/2 mv^2).
• Potential energy is stored energy (e.g., gravitational potential energy PE = mgh).
• Conservation of Energy: The total energy of an isolated system remains constant; energy can neither be created nor destroyed, but can change from one form to another.
• Momentum is the product of mass and velocity (p = mv).
• Conservation of Momentum: In a closed system, the total momentum remains constant if no external forces act on it.
• Rotational Motion describes the motion of rotating bodies, including angular displacement, angular velocity, angular acceleration, torque, and moment of inertia.

Thermodynamics

• Temperature measures the average kinetic energy of the particles in a substance.
• Heat is the transfer of thermal energy.
• Zeroth Law of Thermodynamics: If two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.
• First Law of Thermodynamics: The change in internal energy of a system is equal to the heat added to the system minus the work done by the system (ΔU = Q - W).
• Second Law of Thermodynamics: The entropy of an isolated system tends to increase over time where entropy is a measure of disorder.
• Third Law of Thermodynamics: As temperature approaches absolute zero, the entropy of a system approaches a minimum or zero value.
• Heat Transfer:
  • Conduction: Transfer of heat through a material by direct contact.
  • Convection: Transfer of heat by the movement of fluids.
  • Radiation: Transfer of heat through electromagnetic waves.

Electromagnetism

• Electric Charge is a fundamental property of matter that causes it to experience a force when placed in an electromagnetic field.
• Electric Field: A region around an electric charge where another charge will experience a force.
• Coulomb's Law describes the force between two point charges (F = k * q1 * q2 / r^2).
• Electric Potential is the electric potential energy per unit charge.
• Capacitance is the ability of a system to store electric charge.
• Electric Current: The rate of flow of electric charge.
• Resistance is the opposition to the flow of electric current: V = IR, where V is voltage, I is current, and R is resistance (Ohm's law).
• Magnetism:
  • Magnetic Field: A region around a magnet or current-carrying conductor where a magnetic force is exerted.
  • Magnetic Force: The force on a moving charge or current-carrying conductor in a magnetic field.
• Electromagnetism is the interaction between electric and magnetic fields.
• Electromagnetic Induction is the production of an electromotive force (EMF) in a conductor when exposed to a changing magnetic field (Faraday's Law).
• Maxwell's Equations: A set of four equations that describe the behavior of electric and magnetic fields and their interactions.
• Electromagnetic Waves: Waves of energy that propagate through space, including radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

Optics

• Reflection is the bouncing of light off a surface.
• Refraction is the bending of light as it passes from one medium to another. Snell's Law describes the relationship between the angles of incidence and refraction.
• Lenses are devices that refract light to form images.
• Interference is the superposition of two or more waves, resulting in constructive (increased amplitude) or destructive (decreased amplitude) interference.
• Diffraction is the bending of waves around obstacles or through apertures.
• Polarization is the alignment of the electric field vectors of light waves in a specific direction.

Quantum Mechanics

• Wave-Particle Duality is the concept that particles can exhibit wave-like properties and waves can exhibit particle-like properties.
• Quantization is the concept that energy, momentum, and other physical quantities are restricted to discrete values.
• Heisenberg Uncertainty Principle states that it is impossible to know both the position and momentum of a particle with perfect accuracy.
• Schrödinger Equation: A fundamental equation in quantum mechanics that describes the time evolution of a quantum system.
• Atomic Structure:
  • Energy levels: Electrons in atoms can only occupy specific energy levels.
  • Quantum numbers: Describe the properties of atomic orbitals and electrons.
• Quantum Entanglement is a phenomenon in which two or more particles become linked together such that the state of one particle instantly influences the state of the other, regardless of the distance between them.

Relativity

• Special Relativity:
  • Postulates: The laws of physics are the same for all observers in uniform motion, and the speed of light in a vacuum is the same for all observers, regardless of the motion of the light source.
  • Time Dilation: Time passes slower for moving objects relative to stationary observers.
  • Length Contraction: The length of a moving object appears shorter in the direction of motion relative to stationary observers.
  • Mass Increase: The mass of a moving object increases as its speed approaches the speed of light.
  • Mass-Energy Equivalence: Energy and mass are interchangeable, described by the equation E = mc^2.
• General Relativity:
  • Gravity as Curvature of Spacetime: Mass and energy warp the fabric of spacetime, causing objects to move along curved paths.
  • Gravitational Time Dilation: Time passes slower in regions of stronger gravitational fields.
  • Black Holes: Regions of spacetime where gravity is so strong that nothing, not even light, can escape.
  • Gravitational Waves: Ripples in spacetime caused by accelerating massive objects.