Key Concepts in Physics

Key Concepts in Physics

Fundamental Forces

1. Gravitational Force: Attraction between masses; governs planetary motion.
2. Electromagnetic Force: Interaction between charged particles; responsible for electricity and magnetism.
3. Weak Nuclear Force: Responsible for radioactive decay; plays a key role in nuclear reactions.
4. Strong Nuclear Force: Binds protons and neutrons in atomic nuclei; strongest force at short ranges.

Laws of Motion

1. Newton's First Law: An object in motion stays in motion; an object at rest stays at rest unless acted upon by a net force.
2. Newton's Second Law: F = ma (Force equals mass times acceleration).
3. Newton's Third Law: For every action, there is an equal and opposite reaction.

Energy

1. Kinetic Energy (KE): Energy of motion, calculated as KE = 1/2 mv².
2. Potential Energy (PE): Stored energy due to position, e.g., gravitational PE = mgh.
3. Conservation of Energy: Energy cannot be created or destroyed, only transformed.

Thermodynamics

1. First Law: Energy is conserved; internal energy change equals heat added to the system minus work done by the system.
2. Second Law: Entropy of an isolated system always increases; energy transitions are not 100% efficient.
3. Third Law: As temperature approaches absolute zero, the entropy of a perfect crystal approaches zero.

Waves and Oscillations

1. Wave Properties: Wavelength, frequency, amplitude, speed.
2. Types of Waves:
   • Transverse: Oscillation perpendicular to direction of travel (e.g., light waves).
   • Longitudinal: Oscillation parallel to direction of travel (e.g., sound waves).
3. Interference: Superposition of waves can lead to constructive (amplifying) or destructive (diminishing) interference.

Electricity and Magnetism

1. Ohm's Law: V = IR (Voltage equals current times resistance).
2. Circuits: Series (current same, voltage divides) vs. parallel (voltage same, current divides).
3. Magnetic Fields: Created by moving charges; influence the motion of other charges.

Modern Physics

1. Quantum Mechanics: Describes physical phenomena at microscopic scales; particle-wave duality, uncertainty principle.
2. Relativity:
   • Special Relativity: Time and space are relative; E = mc².
   • General Relativity: Gravitational fields affect the fabric of spacetime.

Measurement

1. SI Units:
   • Length: meter (m)
   • Mass: kilogram (kg)
   • Time: second (s)
   • Electric Current: ampere (A)
   • Temperature: kelvin (K)
   • Amount of Substance: mole (mol)
   • Luminous Intensity: candela (cd)

Basic Principles of Mechanics

1. Momentum (p): p = mv; conserved in isolated systems.
2. Work (W): W = Fd cos(θ); energy transferred by force.
3. Power (P): P = W/t; rate of doing work.

Fundamental Forces

• Gravitational Force: Causes attraction between masses, essential for planetary motion.
• Electromagnetic Force: Governs interactions between charged particles, fundamental for electricity and magnetism.
• Weak Nuclear Force: Responsible for radioactive decay; crucial in nuclear reactions.
• Strong Nuclear Force: Strongest force at short distances; holds protons and neutrons together in atomic nuclei.

Laws of Motion

• Newton's First Law: Objects maintain their state of motion unless acted upon by an external force.
• Newton's Second Law: Describes the relation between force, mass, and acceleration (F = ma).
• Newton's Third Law: States every action has an equal and opposite reaction.

Energy

• Kinetic Energy (KE): Energy of a moving object, defined by KE = 1/2 mv² where m is mass and v is velocity.
• Potential Energy (PE): Stored energy due to an object's position, exemplified by gravitational PE = mgh.
• Conservation of Energy: Principle that energy can neither be created nor destroyed; only transformed from one form to another.

Thermodynamics

• First Law: Energy conservation principle where the change in internal energy equals heat added minus work done by the system.
• Second Law: States entropy increases in isolated systems, indicating inefficiency in energy transitions.
• Third Law: As temperature approaches absolute zero, a perfect crystal's entropy approaches zero.

Waves and Oscillations

• Wave Properties: Include characteristics such as wavelength, frequency, amplitude, and speed.
• Types of Waves: Transverse waves oscillate perpendicular to their travel direction (e.g., light), while longitudinal waves oscillate parallel (e.g., sound).
• Interference: When waves overlap, they can constructively (amplifying effect) or destructively (diminishing effect) interfere.

Electricity and Magnetism

• Ohm's Law: Relates voltage (V), current (I), and resistance (R) through the equation V = IR.
• Circuits: Differentiates between series circuits (same current, divided voltage) and parallel circuits (same voltage, divided current).
• Magnetic Fields: Generated by moving electric charges; they affect the motion of other charges within their influence.

Modern Physics

• Quantum Mechanics: Explains phenomena at microscopic scales, incorporating concepts like particle-wave duality and the uncertainty principle.
• Relativity:
  • Special Relativity: Establishes that time and space are interconnected and relative; E = mc² illustrates mass-energy equivalence.
  • General Relativity: Describes how gravity warps the fabric of spacetime.

Measurement

• SI Units for key measurements include:
  • Length: meter (m)
  • Mass: kilogram (kg)
  • Time: second (s)
  • Electric Current: ampere (A)
  • Temperature: kelvin (K)
  • Amount of Substance: mole (mol)
  • Luminous Intensity: candela (cd)

Basic Principles of Mechanics

• Momentum (p): Defined as p = mv, conserved in isolated systems.
• Work (W): Calculated by W = Fd cos(θ); represents energy transferred when a force is applied over a distance.
• Power (P): Expresses the rate of work done, calculated as P = W/t.