Introduction to Physics: Core Concepts

• Physics is the 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

• Classical mechanics describes the motion of macroscopic objects, from projectiles to parts of machinery, and astronomical objects, such as spacecraft, planets, stars, and galaxies.
• Thermodynamics studies the effects of changes in temperature, pressure, and volume, and of heat transfer in physical systems.
• Electromagnetism studies the interactions of electric currents and magnetic fields.
• Relativity describes the behavior of space, time, and gravity, especially at high speeds.
• Quantum mechanics studies the behavior of matter and energy at the atomic and subatomic levels.

Classical Mechanics

• Kinematics describes the motion of objects without considering the causes of the motion.
• Dynamics describes the motion of objects and the relationship between motion and its causes, especially forces and torques.
• Newton's laws of motion are fundamental principles of classical mechanics:
  • The first law states that 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.
  • The second law states that 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).
  • The third law states that for every action, there is an equal and opposite reaction.
• Conservation laws are fundamental principles that state that certain physical quantities remain constant over time in a closed system:
  • Conservation of energy.
  • Conservation of momentum.
  • Conservation of angular momentum.
• Work is the energy transferred to or from an object by a force causing a displacement of the object.
• Energy is the capacity to do work.
  • Kinetic energy is the energy of motion.
  • Potential energy is the energy stored in an object due to its position or configuration.
• Power is the rate at which work is done or energy is transferred.

Thermodynamics

• Zeroth law of thermodynamics states that if two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other.
• First law of thermodynamics states that energy can neither be created nor destroyed, but can only be changed from one form to another.
• Second law of thermodynamics states that the total entropy of an isolated system can only increase over time.
• Third law of thermodynamics states that as the temperature approaches absolute zero, the entropy of a system approaches a minimum or zero value.
• Heat is the transfer of thermal energy between objects or systems due to a temperature difference.
• Temperature is a measure of the average kinetic energy of the particles in a system.
• Entropy is a measure of the disorder or randomness of a system.

Electromagnetism

• Electric charge is a fundamental property of matter that causes it to experience a force when placed in an electromagnetic field.
• Electric field is a field of force surrounding an electric charge that exerts force on other charges in its vicinity.
• Electric potential is the electric potential energy per unit charge at a specific location in an electric field.
• Capacitance is the ability of a body to store an electrical charge.
• Electric current is the rate of flow of electric charge through a conductor.
• Resistance is the opposition to the flow of electric current through a conductor.
• Magnetism is a phenomenon produced by the motion of electric charges, resulting in attractive and repulsive forces between objects.
• Magnetic field is a field of force surrounding a magnet or electric current that exerts force on other magnets or moving charges in its vicinity.

Relativity

• Special relativity:
  • Postulates that the laws of physics are the same for all observers in uniform motion relative to each other.
  • Postulates that the speed of light in a vacuum is the same for all observers, regardless of the motion of the light source.
  • Time dilation is the phenomenon where time passes slower for an observer who is moving relative to another observer.
  • Length contraction is the phenomenon where the length of an object appears shorter to an observer who is moving relative to the object.
  • Mass-energy equivalence is the concept that mass and energy are interchangeable and can be converted into each other (E=mc^2).
• General relativity:
  • Describes gravity as a curvature of spacetime caused by mass and energy.
  • Predicts the existence of black holes, gravitational waves, and the bending of light around massive objects.

Quantum Mechanics

• Quantization is the concept that certain physical quantities can only take on discrete values.
• Wave-particle duality is the concept that particles can exhibit both wave-like and particle-like properties.
• Uncertainty principle states that it is impossible to know both the position and momentum of a particle with perfect accuracy.
• Quantum entanglement is a phenomenon in which two or more particles become linked together in such a way that the state of one particle instantly influences the state of the other, regardless of the distance between them.
• Quantum field theory combines quantum mechanics with relativity to describe the behavior of elementary particles and forces.