Key Concepts in Physics

Fundamental Forces
- Gravitational Force: Attraction between masses.
- Electromagnetic Force: Interaction between charged particles.
- Strong Nuclear Force: Holds protons and neutrons together in atomic nuclei.
- Weak Nuclear Force: Responsible for radioactive decay.
Newton's Laws of Motion
1. First Law (Inertia): An object at rest stays at rest, and an object in motion stays in motion unless acted upon by a net force.
2. Second Law (F=ma): Force equals mass times acceleration; describes how the velocity of an object changes when it is subjected to an external force.
3. Third Law (Action-Reaction): For every action, there is an equal and opposite reaction.
Energy
- Kinetic Energy: Energy of motion (KE = 1/2 mv²).
- Potential Energy: Stored energy due to position (PE = mgh for gravitational potential energy).
- Conservation of Energy: Energy cannot be created or destroyed, only transformed.
Thermodynamics
- First Law: Energy conservation in thermodynamic processes.
- Second Law: Entropy of an isolated system always increases; heat cannot spontaneously flow from cold to hot.
- Third Law: As temperature approaches absolute zero, the entropy of a perfect crystal approaches zero.
Wave Properties
- Frequency: Number of waves that pass a point per second (measured in Hertz).
- Wavelength: Distance between successive crests of a wave.
- Amplitude: Height of the wave, relates to the energy carried by the wave.
- Wave Speed: v = fλ (speed = frequency × wavelength).
Electricity and Magnetism
- Ohm's Law: V = IR (voltage = current × resistance).
- Electric Field: A field around charged particles that exerts force on other charges.
- Magnetic Field: Created by moving electric charges and magnets; influences other charges and magnets.
Relativity
- Special Relativity: Time and space are relative; time dilation and length contraction occur at high speeds.
- General Relativity: Gravity is a curvature of spacetime caused by mass.
Quantum Mechanics
- Wave-Particle Duality: Particles can exhibit properties of both waves and particles.
- Uncertainty Principle: It’s impossible to simultaneously know both the position and momentum of a particle with absolute certainty.
- Quantum States: Describes the probabilistic behavior of particles.
Important Units
- SI Units: Standard units for measurements (e.g. meter for distance, kilogram for mass, second for time).
- Energy: Joule (J), Power: Watt (W), Force: Newton (N).
Applications of Physics
- Engineering: Principles applied to design structures and systems.
- Medicine: Imaging technologies (e.g., X-rays, MRIs) rely on physics principles.
- Environmental Science: Understanding natural processes (e.g., climate change requires knowledge of thermodynamics).

These concise notes highlight essential topics and principles that form the foundation of physics, aiding in a fundamental understanding of the subject.

Fundamental Forces

Gravitational Force: Attraction between any two objects with mass.
Electromagnetic Force: Interaction between charged particles (electric and magnetic fields).
Strong Nuclear Force: Binds protons and neutrons together in the nucleus of an atom, overcoming electrostatic repulsion, very short range.
Weak Nuclear Force: Causes radioactive decay (beta decay) by changing a neutron into a proton, important for nuclear fusion in the Sun.

Newton's Laws of Motion

First Law (Inertia): An object at rest stays at rest, and an object in motion stays in motion with the same speed and direction unless acted upon by an unbalanced force.
Second Law (F=ma): Force equals mass times acceleration; describes how the velocity of an object changes when it is subjected to an external force.
Third Law (Action-Reaction): For every action (force), there is an equal and opposite reaction.

Energy

Kinetic Energy: Energy of motion (KE = 1/2 mv², where m is mass, v is velocity).
Potential Energy: Stored energy due to an object's position or state (PE = mgh for gravitational potential energy, where m is mass, g is acceleration due to gravity, h is height).
Conservation of Energy: Energy cannot be created or destroyed, only transformed from one form to another (e.g., potential energy converts to kinetic energy as a ball falls).

Thermodynamics

First Law: Energy is conserved in thermodynamic processes (energy can neither be created nor destroyed, only transferred or transformed).
Second Law: Entropy (a measure of disorder) of an isolated system always increases over time; heat cannot spontaneously flow from a cold object to a hotter object without external work.
Third Law: As temperature approaches absolute zero (0 Kelvin), entropy of a perfect crystal approaches zero (the lowest possible energy state).

Wave Properties

Frequency: Number of waves that pass a point per second (measured in Hertz, Hz).
Wavelength: Distance between successive crests of a wave.
Amplitude: The height of a wave, related to the energy carried by the wave.
Wave Speed: v = fλ (speed = frequency × wavelength).

Electricity and Magnetism

Ohm's Law: V = IR (voltage = current × resistance).
Electric Field: A field around charged particles that exerts force on other charges.
Magnetic Field: Created by moving electric charges and magnets; influences other charges and magnets.

Relativity

Special Relativity: Time and space are relative:
- Time Dilation: Time slows down for objects moving at speeds close to the speed of light.
- Length Contraction: Objects appear shorter in the direction of motion when traveling at speeds close to the speed of light.
General Relativity: Gravity is a curvature of spacetime caused by mass; the more mass, the more curvature.

Quantum Mechanics

Wave-Particle Duality: Particles (e.g., light, electrons) can exhibit properties of both waves and particles.
Uncertainty Principle: It’s impossible to simultaneously know both the position and momentum of a particle with absolute certainty.
Quantum States: Describes the probabilistic behavior of particles (e.g., the likelihood of finding an electron at a particular location).

Important Units

SI Units: Standard units for measurements: meter (m) - distance, kilogram (kg) - mass, second (s) - time.
Energy: Joule (J), Power: Watt (W), Force: Newton (N).

Applications of Physics

Engineering: Applications of physics principles in the design and construction of different structures and systems (e.g., bridges, buildings, airplanes).
Medicine: Medical diagnostic and therapeutic tools are based on physics principles (e.g., X-rays, MRIs, lasers, ultrasound).
Environmental Science: Understanding natural processes (e.g., climate change) and developing solutions requires a deep understanding of physical principles.