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.

Core Concepts

• Mechanics: Deals with the motion of bodies under the influence of forces.
• Thermodynamics: Deals with heat and temperature and their relation to energy and work.
• Electromagnetism: Deals with the forces that occur between electrically charged particles.
• Optics: Studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it.
• Quantum Mechanics: Deals with the physical phenomena at microscopic scales, where the action is on the order of the Planck constant.
• Relativity: Includes two interrelated theories by Albert Einstein: special relativity, which deals with the absence of gravity, and general relativity, which describes gravity as a property of the geometry of space-time.

Mechanics

• Kinematics: Describes the motion of objects without considering the causes of motion.
• Dynamics: Deals with the causes of motion, such as forces and torques.
• Newton's Laws of Motion are fundamental principles in classical mechanics.
• Newton's First Law: 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.
• Newton's Second Law: The acceleration of an object is directly proportional to the net force acting on the object, is in the same direction as the net force, and is inversely proportional to the mass of the object (F = ma).
• Newton's Third Law: For every action, there is an equal and opposite reaction.
• Work is the energy transferred to or from an object by means of a force acting on the object.
• Energy is the ability to do work.
• Kinetic energy is the energy of motion. KE = (1/2)mv^2.
• Potential energy is stored energy.
• Gravitational potential energy: PE = mgh, where m is mass, g is the acceleration due to gravity, and h is height.
• Conservation of Energy: In a closed system, the total energy remains constant.
• Momentum is the product of mass and velocity. p = mv.
• Conservation of Momentum: In a closed system, the total momentum remains constant.

Thermodynamics

• Temperature is a measure of the average kinetic energy of the particles in a substance.
• Heat is the transfer of energy between objects or systems due to a temperature difference.
• Zeroth Law of Thermodynamics: If two systems are separately 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 total entropy of an isolated system can only increase over time or remain constant in ideal cases where the system is in a steady state or undergoing a reversible process.
• Entropy is a measure of the disorder or randomness of a system.
• Third Law of Thermodynamics: As the temperature approaches absolute zero, the entropy of a system approaches a minimum or zero value.
• Heat transfer mechanisms include conduction, convection, and radiation.
• Conduction is the transfer of heat through a material by direct contact.
• Convection is the transfer of heat by the movement of fluids (liquids or gases).
• Radiation is the transfer of heat by electromagnetic waves.

Electromagnetism

• Electric charge is a fundamental property of matter that causes it to experience a force when placed in an electromagnetic field.
• Coulomb's Law: The force between two point charges is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance between them.
• Electric field is the region around an electrically charged object in which a force is exerted on other charged objects.
• Electric potential is the electric potential energy per unit charge at a specific location.
• Capacitance is the ability of a body to store an electrical charge.
• Current is the rate of flow of electric charge.
• Resistance is the opposition to the flow of electric current.
• Ohm's Law: The voltage across a resistor is directly proportional to the current flowing through it (V = IR).
• Magnetism is a force caused by the motion of electric charges.
• Magnetic field is the region around a magnet or current-carrying wire in which a magnetic force is exerted.
• Electromagnetic induction is the production of an electromotive force (voltage) across an electrical conductor in a changing magnetic field.
• Maxwell's Equations describe the behavior of electric and magnetic fields and their interactions.
• Electromagnetic waves are disturbances in electric and magnetic fields that propagate through space.

Optics

• Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated.
• Refraction is the change in direction of a wavefront as it passes from one medium to another.
• Snell's Law describes the relationship between the angles of incidence and refraction when light passes between two different media.
• Lenses are optical devices that refract light to focus or diverge an image.
• Diffraction is the bending of waves around obstacles or through apertures.
• Interference is the superposition of two or more waves, resulting in a new wave pattern.
• Polarization is a property of transverse waves that specifies the geometrical orientation of the oscillations.
• The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation.

Quantum Mechanics

• Quantization: Energy, momentum, and other physical quantities are quantized, meaning they can only take on discrete values.
• Wave-particle duality: Particles can exhibit wave-like properties, and waves can exhibit particle-like properties.
• Heisenberg's Uncertainty Principle: It is impossible to know both the position and momentum of a particle with perfect accuracy.
• Schrödinger equation: A mathematical equation that describes the time evolution of quantum mechanical systems.
• Quantum entanglement: A quantum mechanical phenomenon in which the quantum states of two or more objects are linked together in such a way that one object instantaneously influences the other, regardless of the distance between them.

Relativity

• Special Relativity deals with the relationship between space and time for observers moving at constant velocities.
• Postulates of Special Relativity:
  • The laws of physics are the same for all observers in uniform motion relative to each other.
  • 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.
• Mass-energy equivalence: Energy and mass are interchangeable (E = mc^2).
• General Relativity extends special relativity to include gravity.
• Gravity is described as the curvature of spacetime caused by mass and energy.
• Gravitational time dilation: Time passes slower in stronger gravitational fields.
• Gravitational lensing: The bending of light around massive objects due to gravity.