Key Concepts in Physics

Key Concepts in Physics

Fundamental Forces

1. Gravitational Force

   • Attraction between two masses.
   • Described by Newton's Law of Universal Gravitation.

2. Electromagnetic Force

   • Interaction between charged particles.
   • Governs electricity and magnetism.

3. Strong Nuclear Force

   • Binds protons and neutrons in an atomic nucleus.
   • Strongest of the four fundamental forces.

4. Weak Nuclear Force

   • Responsible for radioactive decay.
   • Plays a role in nuclear fusion.

Laws of Motion

1. Newton's First Law (Inertia)

   • An object at rest stays at rest; an object in motion stays in motion unless acted upon by a net external force.

2. Newton's Second Law (F=ma)

   • Force equals mass times acceleration.
   • Indicates how the velocity of an object changes when it is subjected to an external force.

3. Newton's Third Law (Action-Reaction)

   • For every action, there is an equal and opposite reaction.

Energy

1. Kinetic Energy (KE)

   • Energy of motion: KE = 1/2 mv² (m = mass, v = velocity).

2. Potential Energy (PE)

   • Energy stored due to position: PE = mgh (m = mass, g = acceleration due to gravity, h = height).

3. Conservation of Energy

   • Energy cannot be created or destroyed, only transformed from one form to another.

Thermodynamics

1. First Law of Thermodynamics

   • Energy conservation: ΔU = Q - W (U = internal energy, Q = heat added, W = work done by the system).

2. Second Law of Thermodynamics

   • Entropy of an isolated system always increases; energy systems tend to become less organized.

3. Heat Transfer

   • Conduction: Direct contact transfer.
   • Convection: Fluid movement.
   • Radiation: Emission of energy as electromagnetic waves.

Waves and Oscillations

1. Wave Properties

   • Amplitude, wavelength, frequency, speed.
   • Types: Transverse (e.g., light waves) and longitudinal (e.g., sound waves).

2. Simple Harmonic Motion

   • Motion that repeats in a regular cycle (e.g., pendulums, springs).

Electricity and Magnetism

1. Ohm’s Law

   • V = IR (V = voltage, I = current, R = resistance).

2. Circuits

   • Series and parallel configurations affect voltage, current, and resistance.

3. Magnetic Fields

   • Produced by moving charges and magnets.
   • Direction follows the right-hand rule.

Modern Physics

1. Theory of Relativity

   • Special relativity: Time and space are relative; speed of light is constant.
   • General relativity: Gravity is a curvature of spacetime.

2. Quantum Mechanics

   • Describes the behavior of particles on the atomic and subatomic levels.
   • Key concepts: wave-particle duality, uncertainty principle, quantization.

Important Units

• Force: Newton (N)
• Energy: Joule (J)
• Power: Watt (W)
• Voltage: Volt (V)
• Current: Ampere (A)
• Resistance: Ohm (Ω)

Fundamental Forces

• Gravitational Force: Attracts objects with mass. Stronger with greater mass and closer objects.
• Electromagnetic Force: Acts on charged particles. Responsible for electricity, magnetism, and light.
• Strong Nuclear Force: Holds protons and neutrons together in the nucleus of an atom. The strongest force.
• Weak Nuclear Force: Causes radioactive decay. Involved in nuclear fusion.

Laws of Motion

• Newton's First Law (Inertia): Objects remain at rest or in motion unless acted on by a force.
• Newton's Second Law (F=ma): The force applied equals the mass of an object multiplied by its acceleration.
• Newton's Third Law (Action-Reaction): For every action, there's an equal and opposite reaction.

Energy

• Kinetic Energy (KE): The energy of motion. KE = 1/2 mv² (m = mass, v = velocity).
• Potential Energy (PE): Stored energy due to position. PE = mgh (m = mass, g = acceleration due to gravity, h = height).
• Conservation of Energy: Energy cannot be created or destroyed; it changes forms.

Thermodynamics

• First Law of Thermodynamics: Energy is conserved: ΔU = Q - W (U = internal energy, Q = heat added, W = work done by the system).
• Second Law of Thermodynamics: Entropy (disorder) always increases in an isolated system.
• Heat Transfer: Conduction (direct contact), Convection (fluid movement), Radiation (electromagnetic waves).

Waves and Oscillations

• Wave Properties: Amplitude (height), wavelength (distance between wave peaks), frequency (number of waves per second), speed.
• Simple Harmonic Motion: Repeating, cyclical motion like a pendulum or spring.

Electricity and Magnetism

• Ohm's Law: Relates voltage, current, and resistance: V = IR (V = voltage, I = current, R = resistance).
• Circuits: Series and parallel configurations affect voltage, current, and resistance.
• Magnetic Fields: Created by moving charges and magnets. Direction determined by the right-hand rule.

Modern Physics

• Theory of Relativity:
  • Special Relativity: Time and space are relative; the speed of light is constant.
  • General Relativity: Gravity is a curvature of spacetime.
• Quantum Mechanics: Describes the behavior of particles at the atomic and subatomic level. Key concepts: wave-particle duality, uncertainty principle, quantization.

Important Units

• Force: Newton (N)
• Energy: Joule (J)
• Power: Watt (W)
• Voltage: Volt (V)
• Current: Ampere (A)
• Resistance: Ohm (Ω)