Key Concepts in Physics

Key Concepts in Physics

Fundamental Forces

1. Gravitational Force

   • Attractive force between masses.
   • Weakest of the four fundamental forces.

2. Electromagnetic Force

   • Acts between charged particles.
   • Responsible for electricity, magnetism, and light.

3. Strong Nuclear Force

   • Holds protons and neutrons together in the nucleus.
   • Strongest force, but acts over very short distances.

4. Weak Nuclear Force

   • Responsible for radioactive decay.
   • Involved in nuclear reactions.

Classical Mechanics

• Newton's Laws of Motion

  1. An object at rest stays at rest; an object in motion remains in motion unless acted upon.
  2. F = ma (Force equals mass times acceleration).
  3. For every action, there is an equal and opposite reaction.

• Kinematics

  • Study of motion without considering forces.
  • Key equations relate displacement, velocity, acceleration, and time.

Thermodynamics

• Laws of Thermodynamics

  1. Energy cannot be created or destroyed (conservation of energy).
  2. Entropy of an isolated system always increases.
  3. Absolute zero cannot be reached.

• Heat Transfer

  • Methods: conduction, convection, and radiation.

Waves and Oscillations

• Wave Properties

  • Wavelength, frequency, amplitude, speed.
  • Types: mechanical (require medium) and electromagnetic (do not require medium).

• Sound Waves

  • Longitudinal waves that travel through a medium.
  • Speed depends on the medium (faster in solids).

Electricity and Magnetism

• Ohm's Law

  • V = IR (Voltage equals current times resistance).

• Electric Fields

  • Region around a charged object where the object exerts a force on other charges.

• Magnetic Fields

  • Produced by moving charges (currents).
  • Can affect other moving charges.

Modern Physics

• Theory of Relativity

  • Special Relativity: Time and space are relative; mass-energy equivalence E=mc².
  • General Relativity: Gravity is the curvature of spacetime.

• Quantum Mechanics

  • Describes behavior of particles at atomic and subatomic levels.
  • Key principles: wave-particle duality, uncertainty principle.

Applications of Physics

• Engineering: Design of structures, machines, and systems.
• Technology: Development of electronics, communication systems, and renewable energy.
• Medical Physics: Imaging techniques (MRI, X-rays) and radiation therapy.

Important Constants

• Speed of Light (c): ~3 x 10^8 m/s
• Gravitational Constant (G): 6.674 x 10^-11 N(m/kg)²
• Planck's Constant (h): 6.626 x 10^-34 Js

Units of Measurement

• SI Units
  • Length: meter (m)
  • Mass: kilogram (kg)
  • Time: second (s)
  • Force: Newton (N)
  • Energy: Joule (J)

Fundamental Forces

• Gravitational Force: Attraction between masses; weakest of the four fundamental forces.
• Electromagnetic Force: Acts on charged particles; governs electricity, magnetism, and light phenomena.
• Strong Nuclear Force: Binds protons and neutrons in atomic nuclei; strongest force but effective only at very short ranges.
• Weak Nuclear Force: Facilitates radioactive decay and nuclear reactions.

Classical Mechanics

• Newton's Laws of Motion:
  • An object remains at rest or in uniform motion unless acted upon by an external force.
  • Force is calculated as the product of mass and acceleration (F = ma).
  • Every action has an equal and opposite reaction, ensuring conservation of momentum.
• Kinematics:
  • Study of motion devoid of force consideration; includes essential equations for displacement, velocity, acceleration, and time variables.

Thermodynamics

• Laws of Thermodynamics:
  • Energy conservation principle: energy cannot be created or destroyed.
  • Entropy in an isolated system will always increase, indicating disorder.
  • Absolute zero (0 Kelvin) is unattainable, as molecular motion ceases at this temperature.
• Heat Transfer:
  • Occurs via conduction (direct contact), convection (fluid movement), and radiation (electromagnetic waves).

Waves and Oscillations

• Wave Properties:
  • Characteristics include wavelength, frequency, amplitude, and speed; distinguish between mechanical (require a medium) and electromagnetic waves (do not require a medium).
• Sound Waves:
  • Longitudinal waves requiring a medium for propagation; speed increases in denser materials like solids.

Electricity and Magnetism

• Ohm's Law:
  • Voltage (V) is the product of current (I) and resistance (R) expressed as V = IR.
• Electric Fields:
  • Areas around charged objects where they exert forces on other charges.
• Magnetic Fields:
  • Generated by moving charges (currents) and can influence the motion of other charges.

Modern Physics

• Theory of Relativity:
  • Special Relativity posits that time and space are interconnected and relative, with E=mc² representing mass-energy equivalence.
  • General Relativity describes gravity as the curvature of spacetime.
• Quantum Mechanics:
  • Governs behaviors of particles at atomic and subatomic levels; key concepts include wave-particle duality and the uncertainty principle.

Applications of Physics

• Engineering: Involves designing structures, machinery, and complex systems.
• Technology: Focuses on developing electronics, communication infrastructure, and sustainable energy solutions.
• Medical Physics: Encompasses imaging technologies like MRI and X-rays, as well as radiation therapy techniques.

Important Constants

• Speed of Light (c): Approximately 3 x 10^8 m/s.
• Gravitational Constant (G): 6.674 x 10^-11 N(m/kg)².
• Planck's Constant (h): 6.626 x 10^-34 Js.

Units of Measurement

• SI Units:
  • Length: meter (m).
  • Mass: kilogram (kg).
  • Time: second (s).
  • Force: Newton (N).
  • Energy: Joule (J).