Physics Lecture Notes

Introduction

• We're on a rock, floating in space, surrounded by rocks, gas, and nothing.
• Introduction to understanding the universe through physics.

Gravity and Newton

Isaac Newton

• Introduced the concept of gravity and forces.
• Key Formula: Force = Mass × Acceleration
  • Force: Push or pull in a direction.
  • Mass: Amount of matter in an object; measure of inertia.
  • Acceleration: How fast velocity changes over time.

Law of Universal Gravitation

• Two masses attract, described by the Law of Universal Gravitation.
  • Attraction depends on mass and distance.
  • Inverse-Square Law: As distance increases, force decreases exponentially.

Planetary Motion

• Planets orbit the sun due to initial velocity and gravitational pull.
• Most orbits are elliptical, not perfectly round.

Mass vs. Weight

• Mass: Same on different planets.
• Weight: Varies based on gravitational pull (e.g. Earth vs. Moon).

Energy and Work

Types of Energy

• Kinetic Energy: Energy of movement.
• Potential Energy: Stored energy based on position.

Work

• Definition: Force applied over a distance.
  • Example: Lifting an apple.
• Energy cannot be created or destroyed, only converted (Conservation of Energy).

Energy Transfer

• Example of a car stopping: Kinetic energy converts to heat through friction.
• Temperature = Average kinetic energy of atoms.

Thermodynamics and Entropy

• Entropy: Measure of disorder in a system.
  • Example: Ice melting into water increases entropy.
• The universe tends towards higher entropy, explaining the direction of time.

Electricity and Electromagnetism

Electric Charge

• Charges can be positive, negative, or neutral.
• Current: Flow of electrons.
• Voltage: Energy difference pushing electrons.
• Resistance: Measure of difficulty for current to flow.

Maxwell's Equations

• Describe how electric and magnetic fields interact.
  • Moving charges create magnetic fields and vice versa (induction).

Atomic Structure

Atoms and Subatomic Particles

• Atoms consist of protons, neutrons, and electrons.
• Protons/Neutrons: Made of quarks.
• Different elements depend on the number of protons.

Radioactivity

• Unstable isotopes release ionizing radiation.
• Half-life: Time for half of a sample to decay.

Light and Relativity

Speed of Light

• Light travels at 299,792,458 m/s in a vacuum.
• Light behaves as both a wave and a particle (photons).

Einstein's Theory of Relativity

• Speed of light is constant for all observers.
• Mass and energy are interchangeable (E=mc²).
• Gravity is a result of mass bending spacetime.

Nuclear Reactions

Fission and Fusion

• Fission: Splitting of atomic nuclei.
• Fusion: Combining of atomic nuclei.
• Both processes release large amounts of energy.

Quantum Mechanics

Wave-Particle Duality

• Particles exhibit both wave and particle properties.
• Superposition: Particles exist in multiple states until measured.

Heisenberg's Uncertainty Principle

• Impossible to know both precise position and momentum of particles simultaneously.

The Double Slit Experiment

• Light behaves as a wave and particle; interference pattern appears when not observed.

Conclusion

• Physics explores the fundamental principles of the universe.
• Encouragement to engage with the material and learn more.